What kind of testing have you had done other than the urine test? Have they done any imaging? A prostate exam? Have you had prostatitis before?
How old are you?
Unfortunately, you can't get an accurate test result while on antibiotics. You'll have to wait 3 weeks after finishing them.
You're correct that oral is lower risk than vaginal or anal. Were you on the antibiotics when you received the oral? That may help prevent an infection, too.