First baby in a dead end marriage

I'm a new mom to an 8-month-old baby, and I've been struggling in a rocky marriage for the past four years. Despite my hopes for improvement, things have only gotten worse. Our issues began with a high-conflict blended family dynamic, as he has two teenagers, and I'm navigating motherhood for the first time. On top of that, he deals with severe depression, and I've devoted myself to supporting him, but I see no signs of hope. Our communication is minimal, and we have a very dull, roommate-like relationship that I find unbearable. I'm terrified of making the decision to end things, and the thought of being a single mom is overwhelming. I just want to feel like a human again. My life feels incredibly difficult right now.