[Zxcvbn66]

hi everyone, i got a problem and i need some help... my girl friend last menstruation came on the 5th of April and we did a test kit check today and found out that she is pregnant... the problem is before the 1st of April she was together with another guy...after that she was with me... so now i dont't know if she is pregnant with my baby or isit that guy's baby... is it that since her last menstruation came after she is no longer with that guy, there is no possibility that the baby belongs to that guy?