Sex Question (I'm probably stupid)

Hey guys, sorry if this is odd to ask but I just started taking birth control and have been on it for 7 days as of today, and I also just finished my period today. I had unprotected sex with my boyfriend, and although he didn't come inside me I'm a little nervous, does anyone know the probability of pregnancy? I think my birth control should be affective by this point, and I did just finish my period, but I'd really like to hear what other people think. Thank you so much!