All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
If the vows that you took are conditional upon the occurrence of a certain matter and this matter actually took place, or if those vows are not conditional on anything, then you are committed to fulfill them. You have to fulfill the vows—with all their kinds—that you remember and that you are able to fulfill according to you capability. You should offer an expiation for oath breaking for each vow that you are permanently unable to fulfill. The same ruling applies to the vows that you forgot. That is to say, you have to offer expiations for vows of which you are certain that you took them but of which you no longer remember what you exactly vowed to do. This is because, in such a case, the vow is considered unachievable. You have to offer expiations until you believe that you have most likely been cleared of your liability.
Please note that making a vow is disliked because it was authentically narrated that the Prophet, sallallaahu ‘alayhi wa sallam, forbade it. Thus, avoid frequent vowing or, rather, never take vows at all.
Allaah Knows best.