What Causes Painful Red Bumps On Stomach And Thigh Post Intercourse?

Yes so about a week ago I had unprotected sex with a sex partner and now I have these red bumps that start of red but end up as a white head looking thing. They are spreading on to my belly and thigh. Also I have noticed them to be on my penis head and my penis head is very dry. Some of these bumps itch and some are painful but painful as like a pimple pain. I am unsure what the problem is and have no clue what's going on.