3 weeks ago I woke up from sleeping in a youth hostel bed with red patches on my penis just below my penis head and on the head. Sometimes while cold in bed I put my hands in my boxer shorts while trying to sleep and I distinctly remember doing so that night. I washed and they went away within a few hours. In the weeks that have followed they've only ever came back after sexual contact, masturbation and worst immediately after sex.
A week after waking up in the hostel I started feeling slight itches in my pubic hair on my groin and on my scrotum. I've been using a shower emollient on these areas and after few days the itchiness has pretty much subsided. I've seen some dry skin on the sides of my scrotum and also on my foreskin after masturbation.
This morning I had sex with my partner, without a condom and the red patches has appeared again. They don't hurt or itch, perhaps just a slight burning.