I was 3 weeks pregnanton dec 12 2017 when i slept with another guy could he be the father to my baby or is it my husbands my LMP was November 21st 2017 due date is aug 26 or 28 2018
I just want to be sure you know, even if you were pregnant by one day, later sex does not change anything. The egg, penetrated by one sperm, instantly throws up an impermeable shield, and no other sperm can get in (not even one from the same guy with the same ejaculation). This is for the biological protection of the developing embryo. So, don't worry that even in really early pregnancy a subsequent sexual act will change anything at all about the baby that has just begin.