why does it get worse, will it ever get better?

As some of you may heave read one of my earlier posts.  I found out last year that my husband had/and still is having an affair with a former  friend of mine.  It appeared that we were at least making some small steps.  We were at least civil to each other.  I have stepped back and learned so much about ADD (he was just diagnosed this past spring). I understand why he behaves the way he does. I have given him support, space, I do not nag.  I have worked a lot on myself and my bad behaviors.  I do not let him engage me..I have realized it takes 2 to fight.  We have two small boys, one of which has ADD.  I am very willingly to work things out.

My husband just started seeing an ADD psychiatrist.  Since that time he has become withdrawn from me.  Very short tempered to me and the boys.  He blames  me and his parents has even more so than before.  We use to do couples counseling, now he says it is a waste, because he wants a divorce.  Two weeks ago, he said no to the divorce...he admitted to being scared of being divorced and scared of being single.  AS YYZ explained to me, I understanding he is planning the "great escape" for it is much easier to do than to take ownership of one's actions.  I also realize that staying married will be  a lot of work, and that may also scare my DH.

Has anyone experienced this? He appears so angry toward everyone.  He made a comment yesterday that "when things get bad, it is okay to walk away", meaning that is the lesson he will teach the boys.  As opposed to "when things are bad, you work together to resolve it". I have learned to not expect anything so as not to be disappointed.  I am fooling myself to think that my husband will ever see anything positive in me and our marriage and want to work on our marriage?