My period came as expected and towards the very end of it, my boyfriend and I had sex. Normally we don't so soon. We use a condom everytime. Well, it seems that my period had stayed a day longer then expected and now I have this sour odour along with brown discharge. I put a tampon in for a bit just to make sure I still wasn't on my period, and when I took it out I could really smell the foul odour? I'm 17 and haven't been to a gyno, ever, what should I do?