I love the advice given above. If you're hesitant to reach out for assistance please also consider a blog, or talking to a trusted friend. I often just sit down and write things out - which gives me a sense of release. We're only human and can only handle so much. My hubby gives me time to "cry it out" and basically that's me writing it down and throwing it away.
Get rid of the marriage?
Just joking. Get counseling, either together or alone. If you can't afford counseling, see a member of the clergy. Bringing a baby into a marriage that is already stressed is not a way to make it calmer, so it really is imperative to work on the marriage now.
Good luck, sweetheart.