What is the ruling on previous prayers performed by a person suffering from hemorrhoids, with a slight discharge of fluid after ablution, and does this affect the validity of Hajj and Umrah, especially with the presence of obsessive-compulsive disorder?

If the fluid comes out from inside the anus, it is impure and invalidates ablution. One must perform ablution after it stops. If its discharge is unknown, then one must perform ablution for every prayer after its time has begun, like someone afflicted with incontinence (sāḥib al-salas).

As for the past prayers you performed without purification: if you were afflicted with incontinence, your prayer is valid according to the Malikis. If you were not, you are not required to repeat them, according to the choice of Ibn Taymiyyah, and you may adopt this view given the presence of scrupulousness (waswasah).

The Hajj is valid, even if the circumambulation (ṭawāf) was performed without purification, as many scholars do not stipulate purity for the validity of ṭawāf.

Acting upon a weaker opinion after an act has occurred and its rectification is difficult is permissible, and you must disregard the whispers of waswasah.