could be jock itch as well, with it being very hot. Dont know just dont let it go too long without seeing someone
I think you have eczema, which is common, if not 'normal.' It is not related to sex. You shouldn't just live with it, though, because it's awfully annoying and makes you want to scratch all the time. So visit a dermatologist, who should be able to diagnose and treat it in a single visit. You can't cure this, but you certainly can get what you need to suppress it when it comes, so it won't bother you.
Take care.
Dr. Rockoff