Scarleteen

I posted about being afraid of a pregnancy with 3 negative pregnancy tests, even though I took a plan B, had those negative tests with one of them being a doctor's test, and I also did HAVE a period, and now I'm on birth control.... but the more I think about it, I could very well have gotten an STD from the guy I had sex with since he's kind of a player... Anway I guess my question is, why is my period 15 days late and could it be an STD?

Have you seen this article? M.I.A or, Dude, Where's My Period?
We really can't know why your period's late, just because there can be many potential causes, but STIs aren't generally going to be a culprit in upsetting your cycle. It is a good idea, though, to go ahead and get started on regular STI testing, if that's not something you're doing already.