L.W.
I'm sorry that ya'll are going through a hard time. Would ya'll be willing to go to counseling? They will have a lot of good tools for ya'll to try. If he isn't willing, maybe you ought to go on your own to help you work through what you need and want out of the marriage. If you can't afford it, are you involved in church? If so, maybe they can help you. Or there are some places that offer counseling services on a sliding scale. Don't feel too bad about arguing in front of the kids. It happens sometimes, just make sure it doesn't happen all the time. Next time you see it getting heated nip it in the bud and say we'll discuss this later and walk away. Hang in there and good luck!
BTW, congratulations on the new little one coming. :)