What Causes Penis Shaft Scabbing Lumps And Rash After Unprotected Intercourse?

Hi, I have been dating a girl for a few months now and have had unprotected sex quite often. About 3 days ago i broke out with scabbing red bumps, like a rash on the shaft of my penis. It seems to be spreading a little day by day. It doesnt really itch much. They first appeared moist but u have been cleaning it a few times a day with antiseptic spray or hydogen peroxide so it has dryed some but still seem to be spreading. I would also like to inform you i do have exczema which i have read online sometimes can cause this rash, but im 30 years old and have never had this happen before. Would you happen to know whats most likely the cause of this rash?0