Okay so I had a period Oct 13-19. I stopped my birth control Oct. 27 then got another period Oct 30-Nov 5. Exactly 4 weeks from the start day of Oct was this past Fri (Nov 27). I still haven't started. I've taken 2 pregnancy test 2 days apart and both say negative. I have been on the pill for 3 & a half years. Can someone explain?