Crush, Just a quick note--I am so very sorry that you are in this situation, but glad you have found this place. You will find lots of help here.
Thoughts for you: read and reread DR. Also make sure you check out the MLC resources on this forum. There is a whole lot of information on there that will help you. It's hard to say from the brief amount of information in your post whether your H is MLC or just WAH, but it doesn't really change your response. The main thing is that if it is MLC, it is going to be YEARS before he comes out of it, so strap in for a looooooong trip. I'm sorry to have to tell you that, but I don't want to sugar-coat it.
I know your head is spinning and this feels like a nightmare right now. Protect yourself and your children, give yourself time to begin to heal. Do NOT talk to your H about OW, do not bad-mouth him (or her) to your children (or, preferably, to friends or family), do not confront him about anything unless it is very important (pick your battles, and let go of any that are not absolutely crucial), do not cry, beg, demand, pursue, act nasty or rude, or anything like that. This is very important. It is also best if you don't talk to people in your real life (in other words, not here) about what is going on, except for a trusted friend or (preferably) counselor/minister. Don't lie about it, but avoid spilling everything out to anyone and everyone, because it will make things harder for you later. (You may have to practice this mentally in order to avoid just dumping on anyone from your sister to the paper boy.) If you can come up with the fee, sessions with the DB coaches are well worth the expense--I had six sessions with Jody myself, and many others here can testify to how much help a DB coach has been to them.
Oh, and don't wish to hate him. Nothing good will come of that.
When you have occasion to interact with your H, be polite and friendly and non-confrontational. This is going to be really tough when you just want to smack him and yell, "Wake UP! What's WRONG with you???" but you need to keep a lid on that when he's around. When he brings up R stuff or other things that are not neutral issues for you, be as calm as you can, listen and validate where you can. If he asks you to make a decision or discuss something, if possible, politely ask to postpone the discussion to a more convenient time, or to consider your options, or whatever, and then come post here and ask for help if you need it.
GAL (get a life)--this is very important too. Find who you are again, the person who got lost along the way. Make changes that YOU need to make--for YOURSELF. Make sure they are changes that you want to keep for the rest of your life--don't do it just to win him back. Use the motivation triggered by this horror to make those changes that you have known for a while that you needed to make, and make them stick.
I am sure others will come along and give you more helpful advice. I know right now you don't know which end is up and are simply overwhelmed by it all, but I have tried to hit the high points you will need right away. Just do your best, and keep coming here for help.
Take care of yourself...there are lots of good people here to help and support you.
Peace and blessings, Dawn
Me 45/H 47, no kids Together since 1985; M/1992 Bomb1 (EA-OW1, age 22) 2001 Bomb2 (EA/PA-OW2, age 22) 10/2007, A continues H left 11/24/08 minimal contact, no legal action http://tinyurl.com/DawnHope1