What Causes Redness And Burning On Penis After Intercourse?

Hi there, I have a little problem I m kind of uncapable of figuring out. I ve been having sex with this girl for a while, a few months give or take. I took her virginity and I ve had multiple partners in my life time mind you, although I ve never had an std previously in my life with that being said. I ve experienced slight chafing before when I was younger when I may have masturbated too much, including a little marking with some redness and irritation and burning to the touch as if the skin was slightly cut open but not like what I m experiencing now. A reoccurring area got really red and swollen today, after I had intercourse with her and after a few rounds I noticed that it burned with any kind of touching to the area whether it be a vagina or just my fingers and I just need to know what the heck is happening. Please help