I have a serious question my girlfriend or ex girlfriend had sex with me right after her last period. the date we had sex on was january 19th i know that for sure, her period was 3-7 days before that, she missed her period which should have happened last week the week of febuary 16 - 19 around there, but she also had sex with her current boyfriend both unprotected, around valentines day and week before that, who is the father of the child? She doesn't know how far into pregnancy she is but from what i have read and collected i get 5-6 weeks.