Around A Month Ago, I Had Sex With This Girl.

Around a month ago, I had sex with this girl. We didn't really talk about, if any of us had any stds or anything, but since then, the head of my penis has gotten redder. It doesn't hurt or itch, neither have I got any problems with urinating or ejaculating. She put me inside of her, before I got a condom on, so I don't know, if i got something from the five seconds, I was inside of her.. I'm asking here, because I can't seem to find anything about that particular thing anywhere else, and was hoping I could get some help here.