Is contraception effective when my partner cums inside me?

If I take the combined contraceptive pill regularly, at the same time, don't get sick, don't take any "dangerous" drugs that can interfere with the absorption of hormones that protect against pregnancy, and if I don't vomit or have diarrhea, do I have anything to worry about when my partner doesn't inside me? I know it's rather unlikely, but I've got my head pumped up and I'm nervously waiting for the withdrawal bleeding, which I still have a week to get :( Can anyone dispel my doubts? Thank you in advance for your reply.