If you have a child on the way, you don't need to worry about "motivating" him. Are either one of you working?

Your time will soon be taken up with the baby, so I'd let him figure his own stuff out. I happened to read your profile, you are 21 and have been with him for 4 years. And he's bipolar not on medication? Not sounding too promising already.

Stop worrying about him, get your own stuff in order because you will have someone totally dependent on you soon.