I've been wondering about this since it happened but never asked... I've only had period sex twice, and it was with the same girl. We were not really dating but friends with benefits and were both clean, long story short we werent using a condom. I didn't notice anything out of the ordinary (aside from the usual unpleasant details) - but the next morning when I was peeing I noticed on the top of my dick (not the tip, the top of the head, see shitty mspaint below) I had what looked like a friction burn or something. My first thought was an STD or something so I was but it went away within a day and never came back. She wasnt using nuvaring or anything, and we'd had sex a bunch of other times when she wasnt on her period and this never happend. My curiousity has me wondering why this happend or what its from?