What is the ruling on one who suffers from obsessive-compulsive disorder (waswas) before acts of worship, and breaks his oath not to pay attention to it, and does not know the number of times he broke his oath, and how can he atone for that?

Obsessive whisperings (Waswas) are a chronic disease, and the cure is to ignore them and pay them no heed. If oaths are uttered unintentionally or under the influence of Waswas, then nothing is required for them, and there is no expiation, because the person afflicted with Waswas is akin to someone under duress. However, if none of that is the case, then one must determine the number of oaths and expiate for all of them until one's conscience is cleared. The preponderant opinion is that if the subject of the oath is multiple, an expiation is required for each oath.