I got off birth control at the end of July and my periods from August to October were consistent. I had unprotected sex on the last day of my period at the beginning of October and on 19th of October (end of ovulation week according to calendar). My period is 4 days late now. I have taken a pregnancy test a day since the day before my expected period and all negatives. No cramps or any other period systems. Could it be the birth control messing with me? My periods were very irregular before I got on birth control 9 years ago.