I've been preventing for 8months. First time i started with the pills till they were finish then second time went for an injection which lasts for two months. After two months went back to taking ovral pills again and been changing the contraceptives till the past two months. I haven't had my periods for months and thought if i stopped taking them will go on periods but i haven't till now. Note: haven't had unprotected sex since i stopped taking them. What might be the cause of that?