Strange Sensation at tip of Penis?

[GhostFarm]

So two weeks ago exactly I had a drunken one night stand. It was unprotected and I didn't ejaculate. The next day (about 12 hours) after the incident I had a weird tingling/pinching sensation at the meatus or tip of my penis. I can't tell if it's internal or external. I just know the tip is having a strange sensation. I went to the doctors about a week after and had an STD test done for chlamydia and gonnorhea and the results came back negative. The symptoms persisted so I went back in and they tested me again two days after I got the results for the first test. I aired concerns about NGU and a possible UTI, they did another urinalysis and dip test and both came back negative with no signs of bacteria. They gave me a 1g dose of azithromycin and did a physical examination and told me that everything looks good. I took the full dose a little over four days ago. The sensation has gotten a bit better, but it comes and goes. I have no other symptoms of an std, no discharge, no inflammation or redness, and it doesn't hurt when I urinate. It's actually pretty relieving when I urinate.

I'm incredibly stressed out and I don't want to continue making trips to my doctor. The sex was pretty rough. I asked about the possibility of a urethral cut and they told me they would have detected blood in my urine.

Any ideas what this might possibly be?