About 30 days ago, I had unprotected sex while in Brazil. Very soon afterwards, my penis started itching, and over the next few days I felt like I was sweating a lot more in the groin area. There are no visible signs of any kind of any kind of rash or bumps or anything. It still itches and there is a very low level of discomfort at times (sort of just like a hightened sensitivity. I was tested for some of the normal STD's (Chlamydia, Gonorrhea, Syphilis, Herpes Simplex 1&2, Hepatitis B&C, and HIV) and all came back negative. There is no pain or discomfort when I urinate.
I am wondering what it could be? Any suggestions?