I am currently 20wks and 5days pregnant. my due date is july 31st. my last period was nov 1 2012 and only lasted til nov 2. I had sex with my ex nov 3 while I was with my boyfriend and also was having sex with him the whole time. and right after I did my ex me and my bf had sex 2 days later. and im scared I could be pregnant by my ex. I also had a negative test on nov 12. I need help