Need answers

I just started taking birth control the other day. I've educated myself fairly on the subject. But I'm still curious, if there was some sort of accident how would you know if you're pregnant? I'm on the combination pill so I understand that it stops ovulation and you have withdrawal bleeding. But I'm confused on if you were to somehow end up pregnant on bc how would you know. I have high anxiety when it comes to getting pregnant haha thanks in advance!