My bf want his exs baby

I recently went through my bf facebook and saw him writing a girl asking her will she name the baby after him i immediatly questioned him and he said that a girl he use to talk to might be pregnant with his baby, i was devistated he kept this secret from me, she an ex of his that he messed around with while we were on break , if it was his i was going to leave him he even told me he hoped the baby was is! I got pissed off, like why? He says because he really wants a baby it has nothing to do with her im willing to give him a baby, but im in school right now even though the baby turned out to not be his it still really hurt me that he said that even his mom was excited hoping it was his and told me i was over exxagerating but i font think so and now that the babyis not his he asking me for a baby