If you're this unhappy there's a possibility that he is too so if you are comfortable talking to him - figure out a plan to do that. Talk to a lawyer - nothing committal about simply getting advice and getting the potential options laid out. What you do depends on him and how you think he will take this. (1) open to discussion of separation (2) angry, (3) accusatory, (4) sad and begging for forgiveness or another chance (5) a combo. Be prepared for all and how you might react.

I am always an advocate of therapy before making any decisions about divorce. I tried but my husband refuses and has refused for years. I have been going alone and am starting to take the same steps I listed above. If my husband had agreed to therapy a while ago I don't think I'd be where I am now - planning the exit plan. Good luck to you.