Me and my boyfriend had sex on 19th Aug. We had used the withdrawal method and i didn't even take any of those 72 hrs pill. I then had my periods that month on 24th,which was the exact date I should have had my menses. It was relatively painfree and was a normal period. But this month,I am late at the periods by about 12 days. I did 2 home pregnancy test,one on the 6th day of missed period and the other on 9th and both turned out to be -ve. I am almost sure that I did nothing wrong during the test. But till today no sign of my period. I am not sure if there was any precum that night,we again had sex 15mins after he ejaculated,but he was dry,so he didn't bother to clean up. I checked out for all the possible symptoms of pregnancy,and I have none of them,except that I've been having constipation problems for about 2 weeks now and I am not sure if it is due to some other reasons! So,can please somebody help me and tell me if there are any chances of me being pregnant. It has scared the hell out of me.