What Causes Red Rash Around Penis After Unprotected Intercourse?

Question : Hi I am a 21 year old male. 2 weeks ago I had unprotected sex with my partner whom I have been with for 2 months and never used protection. The following morning I woke up and found a painless red ring around my penis, with a few raised bumps where the foreskin folds while flaccid. Soon my testicles started itching along with the inside of my groin. I have had jock itch before and just used some anti fungal cream. After a week the ring started disappearing along with the itching on my testicles but now I have red spotchy discoloration on my penis head but it does not itch or hurt. I continued using anti fungals but it doesn't seem to be helping. I also have an intermentent tingling sensation in my left testicle. Also when this all started I started itching on my lower abdomen above the belt line and looks like a few red spots that do not itch until irritated. I just assume it's the sex but prior to that day I had been wearing (packaged and sealed) under wear that hadn't been washed before wearing. Can you help?