Andy, I just happened upon your post and have been reading your subsequent ones and the responses. Have you seen a doctor yet? You don't sound like a selfish guy to me. But as far as your mental and physical health goes, you need to be. By that, I mean you need to do whatever it takes to get diagnosed. If you are clinically depressed (which is a chemical imbalance in the brain), you may need to get on meds. If the initial ones don't work out, try a different one.
My ex-b.f. (we're more just friends now, though I still love him) started staying home on the sofa all day. He was in a new job as a salesman and had to make cold calls and he stopped doing it. That job was not at all for him and I knew it from the beginning. His brother-in-law had talked him into it and put in a word for him, so he got hired when he was out of a job at the time. He is just not that outgoing or comfortable around strangers. Then he stopped showering and shaving. All he did was lie on the sofa. I had been depressed at one time in my life, and have a family history of depression. In fact, my father, uncle, and paternal g'father all committed suicide. And yet when the problem was that close to me, I didn't recognize it. Thank God, the b.f. went to a doctor when he started having crying jags and his sister and I were afraid for his life. He got a really good psychiatrist. However, he had a hard time finding the right medication. which made him more depressed. We urged him to keep trying, and eventually he found a combination that worked for him. He was diagnosed as clinically depressed, and his psych told him he had probably been depressed all his life and didn't know it. He also had a very bad back, so between that and the depression, he was able to get SSD in his 50s.
Due to my experience with my dad and the b.f., I take depression very seriously. Some people are able to come out of it with counseling; however, others have a chemical imbalance which requires medication for a lifetime. Still others just need short-term medication and therapy to get them out of situational depression. You won't know which category you fit into until you see a doctor and have some blood tests run. See a reputable psychiatrist, even if just for a consult.
I wish you all the luck in the world. If you do what you need to do for you and become happier with yourself, your marriage should improve, too...if that's the only problem.
Hugs,
Connie