I thought I was going to start an in vitro fertilization procedure last month, so you are supposed to start out taking birth control. well I only took one pill and stopped because we decided not to do the procedure until next month. Five days after I took that one pill, which is when I would have ovulated, I began bleeding, like a normal period. It lasted for about 3 days, then stopped. Now it is time for my normal period and it hasn't come yet. Is it possible that that one birth control pill messed up my system enough to make my period late?