Whatever is going on, it isn't an STD. I cannot comment on the diagnosis of prostatitis, but that condition is not sexually acquired. From the negative tests you have had and the lack of response to antibiotic therapy, you can be 100% certain you don't have any infection that will ever harm you, and nothing that can be passed to or harm a sex partner. Your prostatitis may indeed be responsible, but most cases of prostate inflammation like this do not improve on antibiotics and probably are not due to infection at all.
If you were my patient, my advice--assuming I confirmed the previous evaluation by your urologist and the various test results and treatment--would be to follow up with your urologist, as he suggested. But if his further evaluation comes up with no more specific information, you might just have to learn to live with your symptoms, knowing they mean nothing physically important. Somewhere along the line, I might also suggest a mental health evaluation--not because I think you are wacko or because I necessarily believe your symptoms have a psychological origin, but to help decide whether or not emotion is affecting your perception of their severity. (I'm not a believer in pschology creating symptoms out of the blue, but there is no doubt that such factors can powerfully affect how the symptom feels and its severity.)
Not all genital pain, tingling, or other such symptoms means an infection. Psychology often is partly responsible, but this really isn't known well. But it is clear that no harm ever comes from cases like yours. All humans get various aches and pains from time to time, and some people have them all the time: an aching back, unexplained headaches, abdominal discomfort, tingling down a leg, etc, etc. Most people just learn to live with such problems, and most are perfectly capable of doing so, once they become convinced the symptom doesn't mean anything dangerous. Why should the genitals be exempt? Our genitals have a special place in our psyches, but the principle is the same.
This is a common problem in men; you can see several other questions essentially identical to yours. Use the search link to look for 'STD symptoms' and 'STD anxiety'.
Bottom line: Whatever is going on definitely isn't an STD, and that is the limit of my expertise, so I won't be able to offer more comment or advice aside from this response.
Good luck-- HHH, MD
After writing this, the pain in my left testicle went to both and I was in serious pain. Went to the urologist and he did a prostate exam, and the left side of my prostate was inflammed, and the right was fine. He said it is common in men my age...29. Said that I need to sit in a hot tub for 15 minutes a day to get heat in that area, take 600 mg of ibuprofen 3 times a day for the inflammation and 500mg of Levaquin for 10 days and the option to refill if needed. Said that would cause burning during urination. So hopefully this works. Never even heard of prostaitis until now.