question: I recently was taking Tri-Sprintec birth control for four days Dec 20, 2009 i stopped using the pill on the 25th of dec, 2009. bc of the side effects. I had a menstrual cycle jan 5, 2010 which lasted for 6days. Last time i engaged in sex was in Dec of 09. my period is now late, i have taken two preg test which came out negative. bc i stopped the pill on the fourth day is this the reason and my cycle is now messed up.