Expiation for Multiple Broken Oaths
Question

I am short-tempered and quick to swear oaths, and I often break the oaths that I swear. I do not know how many expiations I owe for broken oaths. I want to fulfill what I owe of expiations. What should I do? Is it permissible, in expiation of the oath, to invite family and relatives to lunch? If I swore an oath to divorce my wife (if the oath is broken) and broke it, does that require expiation? Please note that I do not know what my intention was when I swore the oath to divorce my wife, but I think it was most likely that I did not intend to actually divorce her.
Praise be to Allah.Is it OK to swear oaths frequently?
It is disliked to swear oaths frequently, because Allah, may He be exalted, says (interpretation of the meaning): “And do not obey every worthless habitual swearer.” [Al-Qalam 68:10]. This criticism of one who does that implies that what he does is disliked, as Ibn Qudamah (may Allah have mercy on him) stated. (Al-Mughni, 13/439)
Expiation for multiple broken oaths
If a person swore many oaths, and broke them but did not offer an expiation for any of them, then there are two scenarios:

If the many oaths had to do with a single matter, such as if he said: “By Allah, I will not smoke”, then he broke that oath and did not offer an expiation, then he swore the same oath again, then this requires one expiation .
If the oaths had to do with different matters, such as if he said, “By Allah, I will not smoke” , or “By Allah I will not wear (such and such)”, or “By Allah, I will not go to a certain place”, then he broke all of the oaths and he has not offered an expiation for any of them, then does he have to offer one expiation or several? There is a difference of opinion among the Muslim jurists concerning this matter. The majority of scholars are of the view that he must offer several expiations, and this is the correct view, because they were oaths in which he swore to do different things, so each oath is to be considered on its own merits. (See: Al-Mughni, 9/406)

Shaykh Ibn Baz (may Allah have mercy on him) was asked: I am a young man who swore by Allah more than three times that I would repent from a prohibited deed. My question is: do I have to offer an expiation once or three times, and what is my expiation?
He replied: 
“You have to offer one expiation, which is to feed ten poor persons, or to clothe them, or to free a slave. Whoever cannot afford to do that should fast for three days, because Allah, may He be glorified, says (interpretation of the meaning): “Allah will not impose blame upon you for what is meaningless in your oaths, but He will impose blame upon you for [breaking] what you intended of oaths. So its expiation is the feeding of ten needy people from the average of that which you feed your [own] families or clothing them or the freeing of a slave. But whoever cannot find [or afford it] - then a fast of three days [is required]. That is the expiation for oaths when you have sworn. But guard your oaths.” [Al-Ma’idah 5:89]
This applies to any oath that is sworn to do something or refrain from something, even if the oath is sworn (and broken) repeatedly; only one expiation is required, if the individual has not already expiated for the first instance. But if he has already offered an expiation for the first instance, then he swore the oath again, then he must offer a second expiation if he breaks the oath. Similarly, if he swears the oath a third time, and has already offered expiation for the second instance, then he must offer a third expiation (if he breaks the oath again).
However, if he repeatedly swore oaths to do several different things, or to stop doing several different things, then he must offer an expiation for each oath, such as if he said: “By Allah, I will not speak to So and so”, and “By Allah, I will not eat such and such,” and “By Allah, I shall not travel to such and such a place”, or he said: “By Allah, I will surely speak to So and so”, and “By Allah, I shall surely hit him”, and the like.
What is required when feeding the poor (as an expiation) is to give each poor person half a Sa‘ of the local staple food; this is equivalent to approximately one and a half kilograms.
With regard to clothing, it refers to what is sufficient to cover a person when praying, such as a chemise (Thobe) or upper and lower garment (Rida’ and Izar). If he offers them dinner or lunch, that is sufficient, because of the general meaning of the verse quoted above. And Allah is the source of help.” (Majmu` Fatawa Ash-Shaykh Ibn Baz, 23/145)
What happens if you don't know the number of broken oaths
If you are not certain of the number of oaths, then try to work out the approximate number, then offer expiations for that approximate number – if the oaths had to do with different matters – until you think that you most likely have done what is required of you.
Feeding relative as an expiation for broken oaths
If your relatives are poor and needy, and you invite ten of them to lunch or dinner , that will be sufficient as an expiation for your oath, whether you invite them all together or at different times.
Whoever is not able to free a slave, feed poor persons or clothe them, must fast for three days, as mentioned in the verse quoted above.
Does swearing an oath to divorce one’s wife count as divorce?
Swearing an oath to divorce one’s wife is a grave matter , which results in the divorce counting as such if the oath is broken , according to the majority of jurists. Therefore, it is essential to beware of doing that.
Some of these scholars are of the view that it depends on the intention behind the oath. If the intention was to threaten someone, urge her to do something, prevent her from doing something, or prove something to be true or false, then the oath was broken, then he must offer an expiation for breaking the oath . 
However, if he intended to divorce her, then the divorce counts as such. Each person knows his own intention; if he thinks that one of the two matters is most likely to be the case, then he must act according to what he thinks was likely to be the case.
And Allah knows best.