sex and pregnancy help!!!

so me and my boyfriend have sex pretty regularly. I am on the pill so we don't always use condoms. but I've been feeling nauseas lately and I've been peeing a lot more than usual and my boobs are super sensitive. whenever he cums he always pulls out. is there a way that even if he pulls out some could've have still gotten inside of me?? I'm just super nervous I'm only 17 and I need someone else's opinions!