I started Sprintec less than 24 hours (Thursday the 4th) before I was expecting my perido to start. I was getting really nervous because I had unprotected sex 4 days (Sunday the 1st and Saturday the 31st) prior to that. I had all my normal PMS symptoms but I still wasn't bleeding so I just started the pills hoping they would maybe induce my period but instead it never came. I spotted very, very lightly but that's it. Ive also taken an embarrassing amount of pregnancy tests (all negative thus far) but I'm afraid it would still be too early to get an accurate response as its only been 3 weeks and 5 days since my LMP. Although I very regularly menstrate every 14 days.