He is not sure whether he uttered the shahaadatayn, two years after he became Muslim
Question

                There is a brother who embraced Islam approximately two years ago, but he cannot remember whether he uttered the shahaadatayn (twin declaration of faith).  He prays and fasts and strives to follow the religion as much as he can .
Praise be to Allah.Firstly: 
We praise 
    Allaah for having guided our brother to Islam, and we ask Him, may He be 
    glorified and exalted, to make him steadfast, strengthen his faith and 
    increase his worship.  
Secondly: 
If this 
    brother is doubting that he uttered the shahaadatayn after two years of 
    fasting, praying and striving to follow the religion as much as he can, this 
    is undoubtedly waswaas (whispers) from the shaytaan who wants to upset him 
    and make him feel anxious and worried. What is definite is that this brother 
    has repeated the shahaadatayn during this lengthy period time after time. 
    Has he not been repeating the adhaan after the muezzin all this time? Has he 
    not said sometimes Laa ilaaha ill-Allaah Muhammad Rasool Allaah? Does 
    he not pray? For in the tashahhud during the prayer he says: I bear witness 
    that there is no god but Allaah and I bear witness that Muhammad is the 
    Messenger of Allaah. 
Moreover the 
    fact that he prays is regarded as entering into Islam. Hence the scholars 
    said of the kaafir: If he prays then he is a Muslim according to the rules, 
    i.e., he is judged to be a Muslim even if he does not utter the 
    shahaadatayn. 
See: 
    al-Sharh al-Mumti’ (2/12) and al-Mawsoo’ah al-Fiqhiyyah (4/272). 
This is also 
    indicated by the report narrated by al-Bukhaari (391) from Anas ibn Maalik 
    (may Allaah be pleased with him) who said: The Messenger of Allaah  
    (peace and blessings of Allaah be upon him) said: “Whoever prays as we pray 
    and faces the same qiblah (direction of prayer) that we face and eats meat 
    slaughtered by us, he is the Muslim.” 
We should 
    beware of waswaas which befalls some people and makes them confused as to 
    whether they said or did something or not, because waswaas is a sickness, 
    and the remedy for it is dhikr (remembering Allaah) and not paying any 
    attention to it. 
See also the 
    answer to question no. 62839. 
And Allaah 
    knows best.