What is the ruling on repeating an action due to obsessive-compulsive disorder after swearing an oath or making a promise not to repeat it? And does saying "except if Allah wills" invalidate the oath or promise? And is expiation obligatory upon forgetting the oath or promise?

You must ignore obsessive thoughts and ask Allah for well-being from them. Stipulating "in shaa Allah" (if Allah wills) in an oath nullifies the expiation for breaking it, provided that the stipulation is connected to the oath, according to the majority of scholars. However, if you do the sworn-against act forgetfully, there is no expiation upon you, according to the majority of scholars. A covenant with Allah is an oath, according to the majority, and breaking it necessitates the expiation for an oath. The expiation for an oath is a choice between feeding or clothing ten needy persons or freeing a slave. If one is unable, then fasting for three days. If oaths are numerous, the expiation multiplies with details. In case the number of oaths is unknown, one should expiate for what is most likely to clear their conscience. An oath is not a cure for obsessive whispering; rather, it increases it.