It's normal that you would feel this way. Don't forget, however, relationships are a two-way street. If he doesn't want to work on your relationship, it's not going to be healthy. I know that marriage is tough but feeling duty-bound to stay in something that has been making you miserable for years is not healthy. Sure, you have to commit to get over the bad patches but so does he and he sounds like he checked out a long time ago.