New to single parenting

So three months ago my husband tells me that I am the reason he is unhappy in life and hes got someone new. We have been married for 12 years, have two boys and a third surprise boy on the way. He just quit on our life together. He moved me out of the house with our boys and is trying to move in his girlfriend and her three children. He has not had a whole lot to do with my pregnancy till now, because I am high risk and have recently started preterm issues along with developing polyhydramnios (too much fluid) I am 26 weeks. Most days I feel almost sane, then he starts his junk about he wants this or that in the divorce and I go nuts. I never wanted to be a single mom, I took my marriage vows seriously, but he does not want to work on anything or talk to me about working on anything. Just keeps telling me to get the attorney and get the divorce over with. So here I am a single mommy to an 11 year old, 3 year old and soon to be sick newborn. Hi everyone.