Shut it down. Not the marriage, but you. Stop doing things for him, and stop being there for his every whim. Show him that you are not a guarantee. He is taking advantage of you and your love and he sees you as a done deal. He doesn't need to try when it comes to you anymore in his mind. He's comfortable. So make him uncomfortable. Start doing things away from him, make plans with friends, get a hobby, start hitting the gym and taking care of yourself, stop caring about what he's doing and how he's acting. When he feels you starting to pull away is when he will have to choose whether to fight for you or let you go. If he fights, then there is a change to save the marriage. See a counselor both individually and together. Do things outside of the house, spend time together outside of your comfort zones (such as your home), ect. If he let's you go, then you have your answer and you can leave without ever having to wonder if you did everything you could to fix the marriage.