Someone please help..

So I've been off of birth control for a little over a month now and I haven't had withdrawl bleeding or a period yet. I had unprotected sex a lot during the month, and have been having symptom of pregnancy but I took a pregnancy test and it was negative. I'm still wondering why my period haven't started yet or why I haven't even had withdrawl bleeding. My periods were regular before I was on birth control. Could stopping it mess up my cycle? Should I be worried?