Hello So Me And My Girlfriend Had Sex. For About

Hello so me and my girlfriend had sex. For about 2 minutes. With a condom. Which did not break. But we are still worried since it slid up at one point that she may possibly get pregnant? She was on her period. She is a virgin and her cherry did not pop. I don't believe the pre cemon that may have been on me. (the boyfriend ) went in contact with her during the point that the condom slid up, but it is a possibility right? I need to know asap.