Prostate pain for 3 months/fatigue for longer/weight loss. could it be bacterial prostatitis or non bacterial or something else?

Seek help: It very well could be some form of infectious prostatitis. But what I would be most worried about is if your reported weight loss is related to this, as this may suggest a possible associated infection in the blood stream too. That weight loss is quite concerning over that period of time. You need an in-person evaluation to better determine what is going on. Best of luck.