in which episode of x files does fox mulder commit suicide/nearly kills himself? 10 points for an answer!!!!!?

You're probably thinking of Gethsemane/Redux/Redux II, which is the Season 4 finale/first two episodes of season 5. Mulder "commits suicide" in Gethsemane because he has just been told everything he's ever believed about aliens and such is a lie, and that Scully was given cancer to make him believe these lies - or so it appears, in reality the dead body in Mulder's apartment is a man called Ostelhoff, who was shot in the face therefore making him unrecognizable. Mulder uses his "suicide" as a way to adopt the identity of Ostelhoff and get into the Department of Defense, where he tries to find a cure for Scully's cancer.

Season 4 Episode 24 Gethsemane