3 year issue. pain in genital are down to anus. all tests negative. saw a few urologists and said all clear. is there any sti that would cause such issues?

This must be the fifth time (or more) answering this question. No STI is a likely cause: believe it and please stop asking! As advised previously, do some internet research about the male chronic pelvic pain syndrome and prostatitis. Start with this: https://en.wikipedia.org/wiki/Chronic_prostatitis/chronic_pelvic_pain_syndrome

In my experience the usual cause of such discomfort is congestion or inflammation of the prostate gland which I assume had been examined by the urologists and no pathology was found. Prostatic massage has been administered to relieve prostate congestion. In the absence of prominent urinary symptoms I doubt STD. You may want to consult a urologist at a university hospital near you.