I was expecting my first child with my girlfriend and her due date is nov 24th, only to find out a week ago she had cheated on me once on Feb 20th with her ex and they didnt use protection so i know her period started on Feb 11th and we had unprotected sex all around the 20th and into march so i was wondering if there is a great possibility that he is the father and i'm not sure how the dates match up with the 20th. I know i'll probably have to wait 9 months to figure out but i was wondering if thats when she was most fertile?