Yeah that is what my dermatologist told me, not an STD, but I have also had a similar experience and I was on Cipro for 3 weeks.
For me my initial symptoms started after also heavy masturbation for 3-5 days following unprotected sexual encounter. Other symptoms but about 3 weeks later my rash started, but I had been on abx for 1 day or so. It came on suddenly actually following ejaculation and has remained since.
I had a similar experience with my prostate and the tests did not turn up anything, yet they still gave me abx. I had a few different tests done pre treatment but none of them turned up anything. I am glad that you sound improved over there.
Update for those of you with something similar. Urologist did a urine test and a prostate test....both came up clean. no infection.
Best guess is I had some sort of low grade prostate infection that was cleared by the cipro regimen. Most likely this was not an STD if cleared by cipro. (I had already tested negative for gonorrhea and chlamydia prior to taking cipro.) The continuing symptoms appear to be related to anxiety. Feel great now.
Would you all agree this was most likely not an STD to begin with?
If you have more questions post on this thread and don't start a new one.
I would say follow up with your Dr. Does not sound like a STD. Can't say if prostate is swollen or not.