I'm with some of the other posters in that I always wonder how a man who has an (ex?) girlfriend/jumpoff/whatever pregnant can so easily move on to start dating another woman and talk about building a life with her when not long ago, he was potentially saying the same to another woman. He's willing to move on THAT quickly? And if she was a jumpoff, then I'm mad that he was careless enough to be raw-dogging it....
Then, if a man is about to become a father, then I'd question his priorities... I'd be expecting him to be focusing on his new child (and by default, the mother of said child), not moving on to the next woman. If he's doing that to someone else, then what "might" he do to me if he gets bored with me? (And hopefully, I wouldn't be pregnant).
Also, folks blame the devil too much for stuff that people do by their own volition. The devil didn't get busy in this situation... ole boy is just a liar (by omission) and perhaps not the great guy he made himself out to be.
I wish you luck in whatever you decide, but I know that one of my rules is not dating a man with a newborn and CERTAINLY not a man who has a baby on the way.