cherry: its hard once pregnancy makes you extra emotional,but keep telling yourself its better to be happy by yourself than miserable with him. and you still need to go through the break up emotions... and its hard when he is there!! i would just tell him to figure his shit out, go stay with a friend or something.
Secondly if that girl his ex agrees to start dating him again while he is about to be a father to your baby she is a bloody idiot!! so that relationship is doomed. And ppl break up for a reason, second time or how many times it is is not gonna make it better. And she is gonna end up being super jealous about the attention he is going to have to give to you, the pregnancy and eventually the baby.
So take a seat and just watch him make stupid ass mistakes. =D