It stops working..what else is it supposed to do! Birth control pills are supposed to be taken everyday and at the same time so say you take it a 7 am its always supposed to be seven once you stop taking them you can definitely get pregnant also, most people get their period since birth control is pretty much hormones that are being released in to your body to fake a pregnancy so that you don't have your period or get pregnant. Thats why there are so many easier contraceptives out there ask your doctor about them.