Too leave or not too leave.. that is the question?

I am so unhappy in my marriage.My husband and I have been married going on 6 years. The past three have been not so good. He has a addiction to the computer and internet games. I played the games with him for a year or so, but it got old when I realized that wasn't the answer.If you cant beat 'em join 'em? He never wants to go anywhere or do anything. He does help me with some housework, but right after he is finished he is right back in that computer chair. The last two nights I told him dinner was ready and he came and got his plate and went and ate in the bedroom at the computer. I wanted to cry, He works full time, although he is late too work about everyday.We have been to marriage counseling 2 sessions. We addressed his computer addiction, and he said he wouldn't spend as much time on it. That didn't last long. He doesn't want too go back to counseling.I feel so lonely and I am married..? I cook, clean, do the shopping, do the errands,laundry, pay bills. I feel like his maid. He doesn't make me laugh. Not much of a sense of humor. He is also 10 years younger than me and I feel alot of the time I am being a mother too him. I have a 23 yr. old son who lives on his own that I have to help take care of as well. My husband resents this, and I can feel he does not care for my son, and that brings tension into the relationship as well. I would have been gone a long time ago, but I am on disability and I have a limited income so I don't know if I could make it on my own. Oh and I am also a devout Christian and my husband is not a believer. This is a huge factor as well. I've tried talking till I'm blue in the face about these issues, and it doesn't do any good.