I been on birth control for a year n thank you for the comments.
So long as you have been taking the birth control for over a month and taking it consistently without missing any days, you should be fine, but there is always room for error whenever humans are involved. Don't stress about it, but if you end up late, take a test.
its always a possibility especially if you let him eject inside of you... odds are you aren't pregnant but if you would be late then take a test it's the only way to know for sure.