How Long Does Sperm Survive Inside The Female Body?

hello, I have a queston: so me and my girlfriend had unprotected sex and I came inside of her, she said it was okay because of the birth control pills, which we've been keeping track of for the past while.

Now here's what's making me a little paranoid because I don't really know everything...assuming that sperm survives inside for 5 to 7 days, and that she's 1 day away from getting her period, what are the chances of her getting pregnant? Or rather, if she does end up getting her period, will she still be able to get pregnant from that same sperm?