impotent partner can make babies??

I know i don't have a normal erection and i admit it's really hard for me to make love with my partner. i had a girl friend and my sex life to her is not really active as like others. every night i try to make love to her but i can't erect my penis. but if there are times that my penis well get erected i always do the best that i can to get cum. but i'm not at my partner is not ready to get pregnat. so we were using a calendar method or widrowal method. but one day i can't prevet it and i get cum inside here vigina. i'm very happy after she told me that she is pregnant. but one day i just found out that my girlfriend having sex with different guy during are relationship. so i just want to know that is there possible that I'm the father of her baby?? does impotent guy can make babies?? looking forward with your reply.