H is back to his mean ways towards me ...trying to find fault in anything that I do...even the way I made a sandwich.

You've no doubt been trying to draw close, in response, he's trying to create distance in your relationship. He's picking on things that are non-essential. There are many ways to make a sandwich. How someone makes a sandwich does not a relationship make, right?

He is back to going to the bar at least three days a week coming to the house between 12 midnight and 4 in the morning.

Again, this is part of his creating distance in your relationship.

if I can leave this marriage behind she thinks that I will be suprised that one day a man will treat me wonderful

That a better love is out there for you is entirely true.

I need to realize that I am not the failure in this relationship and that I have given my all.

You already have that realization. Now the thing to do is act on it.

Why am I so afraid to do anything about it.

That's the key. You fear something(s). What are those fears? Fear of being alone? Fear of facing an uncertain future? Fear of never being loved again?

All those fears are without foundation. Examine them; see why those fears are baseless.

What do you have now? Nothing. You don't have a real relationship. You have a struggle. You're not being loved. You have therefore nothing to lose by moving forward.

Questions I ask myself although I know that I will never know the answers....
1)Why did he have a change for the worse...(getting mean...never like that before)
2)Why did he have the affair...

Gee, I hate to sound like a broken record, but do read "She's Scared, He's Scared". I've been touting that book because it really helped me understand what's going on and that in itself has helped my healing.

The short answer is that your H is acting like the classic active commitment-phobe. As he struggles with his commitment issues, he feels more and more the anxiety of being in the relationship with you, so he creates more and more distance. As he does, your response is to try and draw closer or have him draw closer, and that steps up his anxiety. In turn, he escalates the behavior designed to drive you away and pin you up against the wall so that you break the relationship. He doesn't want to break the relationship because that will add more guilt and pain to him. It's easier to have you break it so that he can blame you for it.

So he steps up his bizarre behavior by being hostile. By picking on "flaws" of yours that have been there all the time (like how you make a sandwich), because it's not anything you really need to change, it's really just him picking on anything and magnifying it. Change the way you make a sandwich, and he'll still find fault, guaranteed.

So he stays out all night. So he has an affair. He just escalates his behavior until you won't put up with it anymore.

What's next? More! Even uglier behavior. Meaner. More abusive. If you don't get out of the relationship, push will come to shove, there will finally come either a major confrontation between you two (and of which, when you tell him to get out, he's going to point his finger at you and say, "See? You don't love me!" or some such take, essentially, blaming it on you. Reminds me of when my WAW admitted she had broken her promise never to contact the OM again, and told me she had started to see him. Now I understand she was telling me this in order for me to break the relationship. And I did that very day, by kicking her out. Do you know she told people that by doing that, I was therefore being "hostile" to her? After she admitted breaking her promises to me, being unfaithful and starting up an affair, that my response to that was a hostile act to her? ) or he's just going to vanish when he reaches his breaking point, leaving you dazed and wondering "WTF happened?"