A new Muslimah is doubtful about the obligation of wearing hijab when praying
Question

Im a new muslim revert. Im wondering how a muslimah is to dress during prayer. It doesn't say to wear hijab during salaat in quran or at least I couldn't find it. Will my prayers still be accepted if I don't wear hijab or something that doesn't cover my body? I wear hijab in public and around men but I know Allah isn't looking at me sexually so why do I have to cover up? When I die I will only be wearing a white sheet and no clothes and when I rise from the grave on judgment day, I will still have no clothes on. When I speak to Allah on judgment day I will be naked so why is it not ok for me to speak to Allah during salaat wearing whatever I want? Allah sees everything and he is my creator so that means he sees me naked all the time. Islam and salaat is supposed to be easy. I feel I'm losing my Iman and I haven't been praying lately because of this issue and I can't find the right answer. I want to pray wearing only my pajamas (short and t-shirt) but I'm afraid something bad will happen to me if I don't wear hijab.
Praise be to Allah.First of all, we would like to congratulate you for the blessing of Islam and faith, and we ask Allah, may He be exalted, to bless you and guide you in this world and the hereafter. 
You should understand that the wise person is the one who is fair-minded and thinks objectively, paying attention to all angles of the matter he is examining, so that he will not fall prey to contradiction: today he finds himself doubting the reason why he should cover up when praying, but if the Sunnah was to be uncovered when praying, he would soon find himself having doubts and questioning the reason why one should uncover oneself too. So when Islam enjoins covering up he objects to it, and if it were to enjoin uncovering he would object, and so on. On this website, we hear about the thoughts of confused and troubled people a great deal, as they are living in a vicious circle to which there is no end unless they block the whispers of the Shaytaan, otherwise the Shaytaan may well impact their religious and worldly affairs. 
All people understand that the issue of clothing differs from one situation to another. The workplace and formal occasions are not like leisure trips or being at home. A person’s situation in this world is not like his situation in the grave, beneath the earth; whoever thinks that these situations should be alike is contradicting sound reasoning, and will end up thinking that these rational standards contradict one another, but his thinking is not based on any rational or shar‘i principles. 
By the same token, in your question you want to compare your situation when standing before Allah in prayer to your situation in the grave or on the Day of resurrection, or to your situation when you are wearing house clothes or pyjamas! Not only that, you think that this wrong analogy is becoming a serious problem in your mind, and a catastrophe that you cannot stop thinking about, to such an extent that doubts have begun to creep into your heart. This is a sign of lack of reasoning which requires you to ponder and think about it, so that you do not let it affect your affairs in this world, let alone the hereafter. 
Fine, if you want to draw analogies, which situations will you choose? 
Would you prefer to pray naked, as your mother bore you and as you will be gathered on the Day of Resurrection? 
Or do you want to pray in a shroud whilst you are still alive in this world, as the deceased is wrapped in his shroud? 
The situation you are looking for is not what Allah has prescribed, neither is it akin to the situation of the deceased in his grave or the situation of people on the Day of Resurrection. You are not following the conclusions of your own analogy or the teachings of Islam. 
Let us say that there is no good reason for all of that, and there is nothing that deserves all this thought or doubts. The matter is far too insignificant for that. If you were to ask any wise person about the wisdom behind Muslim men and women covering when they pray, he would not hesitate to tell you that it is for the purpose of showing respect, being modest and observing proper etiquette before Allah, may He be glorified, when standing before Him and communicating with Him. It is something wonderful to stand before Him, may He be glorified and exalted, when you are fully dressed in the manner that He asks of you and that He loves for you, which is to wear hijab and to cover the head in particular, as well as the rest of the body. Allah, may He be glorified and exalted, says (interpretation of the meaning):
“O Children of Adam! Take your adornment (by wearing your clean clothes), while praying and when going round (the Tawaaf of) the Ka‘bah, and eat and drink but waste not by extravagance, certainly He (Allah) likes not Al-Musrifoon (those who waste by extravagance)”
[al-A‘raaf 7:31].
What is meant by “while praying” is at the time of every prayer, whether it is in the mosque or otherwise. 
Al-‘Allaamah as-Sa‘di (may Allah have mercy on him) said: That is, cover your ‘awrah at the time of all prayers, obligatory or voluntary, for covering it is adornment for the body, whereas uncovering leaves the body unpleasing and off-putting. 
It may be that what is meant by adornment here is more than merely covering, namely clean and proper clothing. This indicates that it is enjoined to cover the ‘awrah when praying and to choose nice clothes for it, and keeping that clothing clean and free of dirt and impurities.
End quote from Tayseer al-Kareem ar-Rahmaan (p. 287) 
Prayer is a serious matter, in which one is standing before Allah; the Muslim slave converses in the prayer with his Lord, focusing his mind and heart on his Lord and Creator, with presence of mind, humility and tranquillity, hoping for His mercy and fearing His punishment; he places his head and nose on the ground in humility before Allah, may He be glorified and exalted. In this important situation, nothing is befitting except for the Muslim man or woman to be completely and properly clothed, in garments that befit a meeting with the King of kings, may He be glorified and exalted, not in night clothes or work clothes. 
Moreover, you have to realise and have a firm belief – as you are a sincere Muslim – that Islam means submitting and surrendering to Allah, may He be glorified and exalted, because of what is mentioned in His holy Book and what is narrated in the Sunnah of His Prophet Muhammad (blessings and peace of Allah be upon him). What the Muslim must do, if he finds himself confused and unable to see the wisdom in any matter, is to seek the light of Revelation which will show him the way; this Revelation which comes from Allah, may He be glorified and exalted, is to be found in the Qur’an and Sunnah. Allah, may He be glorified and exalted, says (interpretation of the meaning):
“O you who believe (in Moosa (Moses) (i.e. Jews) and ‘Eesa (Jesus) (i.e. Christians))! Fear Allah, and believe too in His Messenger (Muhammad (blessings and peace of Allah be upon him)), He will give you a double portion of His Mercy, and He will give you a light by which you shall walk (straight), and He will forgive you. And Allah is Oft-Forgiving, Most Merciful”
[al-Hadeed 57:28]
“Certainly, We have brought to them a Book (the Qur’an) which We have explained in detail with knowledge, - a guidance and a mercy to a people who believe”
[al-A‘raaf 7:52]. 
The Muslim seeks guidance in Islamic teachings, and is not like those of whom Allah, may He be glorified, says (interpretation of the meaning):
“And among men is he who disputes about Allah, without knowledge or guidance, or a Book giving light (from Allah)”
[al-Hajj 22:8].
This is one of the basic meanings of Islam, faith in Allah, may He be glorified and exalted, and belief in His Prophet Muhammad (blessings and peace of Allah be upon him) – not what you are doing of doubting every little thing to the extent that you describe in your question. There is no justification for that, for you could have continued to pray as the Muslims do, then ask whatever questions you wanted to after that; you should not have given in to the whispers and doubts of the Shaytaan and stopped praying altogether. 
The Holy Qur’an is the word of Allah, and the word of Allah is perfect, fair and precise; it has no shortcomings whatsoever. Allah, may He be glorified and exalted, is the One Who says (interpretation of the meaning):
“And whatsoever the Messenger (Muhammad (blessings and peace of Allah be upon him)) gives you, take it, and whatsoever he forbids you, abstain (from it) , and fear Allah. Verily, Allah is Severe in punishment”
[al-Hashr 59:7]. 
The Prophet (blessings and peace of Allah be upon him) instructed women to cover themselves when praying, and to wear hijab and cover their heads. It is proven from ‘Aa’ishah (may Allah be pleased with her) that the Prophet (blessings and peace of Allah be upon him) said: “Allah does not accept the prayer of any woman who menstruates unless (she wears) a head cover.” [What is meant by a “woman who menstruates” here is a woman who has reached the age of menstruation, not a woman who actually has her menses.]
See Ma‘aalim as-Sunan (1/180). Narrated by Abu Dawood in as-Sunan (641); at-Tirmidhi in as-Sunan (277) – he said: It is a hasan hadeeth. The ruling of the scholars based upon this hadeeth is that when a woman reaches the age of puberty, if she prays with any part of her hair uncovered, then her prayer is not valid. 
Ibn al-Mundhir (may Allah have mercy on him) said: 
They were unanimously agreed that the free adult woman must cover her head when she prays, and that if she prays with all of her head uncovered, then she must repeat the prayer.
End quote from al-Ijmaa‘ (p. 43) 
If you do not want to follow the Prophet’s Sunnah with regard to this matter, then why do you pray Zuhr with four rak‘ahs, when you will not find this number in the Book of Allah? Why do you give zakaah at a rate of 2.5%, when you will not find this number in the Qur’an either? In fact the Muslims take all of those numbers from the saheeh Sunnah of the Prophet (blessings and peace of Allah be upon him), for Allah, may He be exalted, says (interpretation of the meaning):
“Nor does he speak of (his own) desire.
It is but a revelation revealed”
[an-Najm 53:3-4]. 
Our scholars (may Allah have mercy on him) said that the verse “while praying” [al-A‘raaf 7:31] is one of the teachings of the Qur’an that helped primitive nations to become civilised. Just as the Arabs during the Jaahiliyyah used to circumambulate the Ka‘bah naked, many nations did not have the culture of wearing clothing and adorning themselves with clothing. By requiring people to dress fully, Islam became one of the means of those nations taking a huge leap forward in terms of civilisation. 
Al-‘Allaamah Muhammad Rasheed Rida (may Allah have mercy on him) said: 
This instruction to wear adornment “while praying” – and not only in al-Masjid al-Haraam – is one of the basic principles that form a sound foundation for a person’s religious and worldly affairs. Some of the value of this principle may be understood from the reports that speak of the reason for revelation of these verses. Indeed, in order to fully appreciate its value we need to know something of the history of nations and religions, and to understand that most wild peoples who live in the bush and in the jungle, as individuals or in groups, and live in caves, and many idol worshipping tribes who live on ocean islands and African mountains all live naked, both women and men. But whenever Islam reached any of these peoples, it taught them to wear clothes by making it obligatory to cover themselves and adorn themselves. When some European missionaries went to extremes in criticising Islam in order to put people off it and turn them away from it, and to incite Europe against the Muslims, one fair-minded person among them responded by reminding them that the spread of Islam in Africa was in fact a blessing to Europe, because it had spread civility among the people by making them give up nakedness and obliging them to wear clothes, and this was the reason for the European textile industry finding a market among them! 
Indeed I say that there are some idol worshipping nations that have a strong civilisation and a high level of various branches of knowledge and the arts, but most of them live naked, but when any of them is guided to Islam, they begin to wear clothes and adorn themselves, then they begin to make clothes. Then their idol-worshipping neighbours begin to imitate them to some extent. Thus we see India, whose civilisation was highly developed in the past and at present, despite the prevalence of idol worship; you still find thousands of their women and men fully naked or half naked or three quarters naked. You see some of the men in stores and factories almost naked, covering only the private parts, or only covering the lower half of the body; and a woman may leave her belly, thighs or the upper part of her body – all or some of it – uncovered. Some of their fair-minded scholars have admitted that the Muslims are the ones who taught them to wear clothes and to eat from vessels. Many of the poor people still put food on leaves and eat from them. But they are better off than many other polytheists in terms of covering and adornments, because the Muslims used to rule them, and Indian Muslims are still among the most advanced Muslims on Earth in terms of knowledge, deeds and influence over the idolaters in their country. 
As for the Muslims further east, where ignorance is prevalent, they are closer to the idolaters than to the Muslims in terms of the way they dress and in many of their religious rituals. An example is the Muslim women of Thailand who do not regard any part of the body as ‘awrah apart from the private parts, as mentioned above. Wherever Islam grows stronger, then you will find that covering and adornment that is befitting of human dignity and civility. 
Whoever understands this will realise the value of this important principle in Islam. Were it not for the fact that this most civilised faith made clothing and adornment part of the religion of Allah – i.e., He made it obligatory upon His slaves – it would not have transformed so many nations and peoples, leading them from extreme wildness to refined civility. The one who does not recognise this blessing is the one who is ignorant of history, even if he claims to have knowledge of it. In fact it is not unlikely to find a westernised pretender who sits in a casino or cafe or pub, leaning back with his hat tilted on his head, saying: What does it mean to say that people should adorn themselves with clothes as part of religious matters, at a time when it is necessary for all humans to cover themselves and there is no need for divine revelation or a religious decree?
End quote from Tafseer al-Manaar (8/340-341) 
On our website we have previously published a number of fatwas which explain how a woman should dress for prayer; please see the following questions: 11073,  69804, 32993
To sum up: 
Prayer in which one stands before Allah is something of great importance which requires the Muslim woman to wear complete hijab, paying attention to proper etiquette before Allah. This is something other than the clothes that one wears at home, which is light clothing. Moreover, the Muslim receives light and guidance from the Holy Qur’an and saheeh Sunnah, so he should not make his views and doubts judge of the revelation that comes from Allah. 
And Allah knows best.