Hi, I have these small red bumps on the head of my penis they show up usually after I have sex, I have unprotected sex with my girlfriend, im 98% sure she has no STD's and that she is clean, but these red spots will show up after sex, and a couple days later look like blisters, I wash it with warm water anytime I can and they end up going away, but they come back after sex again, Is this something I should worry about? Does this sound like an STD?