My last period was February 21st. I have a 41 day cycle I had to get my period yesterday but I didn't. I am one day late. Although I have a 41 day cycle didn't I have to get my period last month? Also the month of march I had unprotected sex with my bf every weekend. According to my charts I was ovulating march 15-22 I was very sexually active on the 21st. I have taken 3 HPT and they were negative. Can there be a chance I can be pregnant?