I had an unprotected one night stand with a guy on October 20th. Three weeks later on November 10th I got my period, normal period that is. My periods are heavy and last 3 to 4 days. On November 20th I had unprotected sex with my boyfriend. We were going through a break which is why I hooked up with the other guy. Nearly four weeks later, today I found out I was pregnant through a pregnancy test. I need to know who the father is.