My due date gong by a 6 wk and 8 wk ultrasound is the 20th Feb 2012. I conceived around the 30th May and my lmp was 16th May. I slept with A guy before I started dating my boyfriend, I slept with this guy at the end of April. But if i conceived end of May, and had my period on the 16th May..wpuld it deff be my boyfriends? I heard sperm can only live for 5 days so that should rule the other guy out right? Xx