Have you read Divorce Busting or Divorce Remedy? They have great advice about how one person can turn a M around. And one of the central themes is working on you. Establishing your goals and following through. I wouldn't move out yet, I think you are making the decision based on emotions and that isn't always the best idea.
If he is hiding things, chances are it is going on. But, it isn't about them, it is about you. Believe nothing that he says and only half of what he does. He is putting the blame on you, he can't handle it.
Dagny
Me 48, H49, M24, S14, S11 DB #1 4/2002-8/2003 Bomb #2 August 2010 & he moved out Living with OW