I have taken this birth control over a year tricycling my period with no problems. Last month I had my period but I started a new pack a day later than I was supposed to. And I had unprotected sex. I still started the new pack. Now this pack is finished and I don't want to start another one until I make sure I'm not pregnant. My last white pill was Sunday night and I haven't started my period yet. I've taken two pregnancy that were negative. Could I be pregnant?