I'm still not clear. Has the doctor diagnosed prostatitis, or have you simply decided that's what's causing the problem? Are you self-diagnosing?
I'm a little baffled by your latest statement that it was "your prostate" that caused pain and prevented you from reaching orgasm. How can you tell it was your protate? I may be wrong, but I'm not sure we actually feel pain from our prostate. Pain of the kind you're describing would seem more likely to originate in the urinary tract: the kidneys, the ureters, the bladder possibly.
Also, when I visit my uro, I always am asked to pee in the cup as soon as I arrive, and by the time the doctor walks into the exam room, he knows whether any kind of infection has been detected in the urine sample. No waiting involved. So, do you know for sure that you have a UTI, or are have you been told that you have an infection, but that the precise strain needs to be identified?
I can understand that you're worried, but self diagnosis can be a worrisome game and usually leads to wrong conclusions. For example, you seem to suspect that the biopsy has caused discomfort in your bowels. That may not be the case at all, though there's certainly a possibility that the antibiotics have caused diarrhea or cramps.
Congratulations on your weight loss. That's quite an accomplishment.