Dr. did prostate rectal exam. it was painful n burning. he said he will wait or hold on antibiotics prescription till i come back in 3 months. why ? what do you think he suspected?

? not infection: The doctor apparently is not suspecting infection. There are other prostate problems that can cause pain on exam. It would be ok to call your doctor's office to ask what they suspect is wrong.

Aseptic prostatitis : Depending on what the urine test showed it's likely aseptic prostatitis which is a benign condition where the prostate gets inflamed for reasons other than an infection. In these cases we like to let the prostate heal before starting on antibiotics. I doubt it was anything serious such as cancer or they would have immediately had your return for ultrasound or biopsy.

Prostatitis: If the physician felt that the prostate gland was tender when he palpated it, he suspected an inflamed gland(prostatitis) which is usually treated with antibiotics. On the other hand, the exam may have simply been uncomfortable either because of poor technique or inadequate relaxation. I don't think that He would wait 3 months if he strongly suspected an infected gland.