I think you should be careful about this relationship.

you said that his ex-girlfriend is pregnant. Is it possible that he is still seeing her and you at the same time? I know you really really like this guy. If you two have a committed relationship and good communication, then this should work out fine, though his ex is pregnant. If you are both committed to this relationship, all of these issues should work themselves out. Is the ex trying to get back in his life again? I think these are questions you should ask him. Does he have other children? I hope things work out between you and him. As long as he's honest with you about him and the ex, then it shouldn't mess up what you and him have. Of course, when the baby's born things will change some, but a lot depends on the type of relationship he has with the ex and if she wants to be with him. Also you said he found out "today" that she's pregnant. When is she due? Also, how did you meet this guy? I hope everything works out. :d