Holy moly... Your situation sounds so much like what I dealt with in my 1st marriage. I didn't want to divorce either, but I'm going to tell you now that only one person working on saving the marriage will NOT save it. It took me 5yrs to get out. Being remarried... I am SO HAPPY now. I am not the person I was with my ex. My ex changed who I was.
Sometimes when people are together, they don't realize they aren't themselves with that other person.
Ask him why he wouldn't want to work on the marriage by seeing a counselor. You can talk to your OB about the PPD. But there are deeper issues than just PPD. I also bluntly asked my ex one day, "What do you expect from me as your wife? I want details on what you want from me."
He didn't have an answer. Because what was he going to say? "I want you to take care of the house, inside and out, cook for me, take care of our daughter, work and make as much money as I do, let me play my computer games from the time I get home from work until I'm ready for you to give yourself to me at 11pm, even though I know you get up far earlier than me, and do everything I ask." Um... No. He would feel guilty for telling the truth... So he had no answer.
If you have any questions... FEEL FREE to PM me.