You need to be able to really talk with someone. The pressure bottled up inside you builds until you feel like you are going to explode.
We are fortunate enough to have a pastor who is a MC. Which helped on numerous points: godly man, knowledgeable, accessible just about any time, and free (because we are beyond broke it seems).
If I were you, I would search for a MC and let them know what is going on. Maybe see the MC together. Just go see someone.
Right now you need to know a very critical thing; this is not your fault. I know you want to say you share some of the blame. For a broken marriage, sure it takes two. An A takes one to walk away from the others. You want to take some measure of blame to try and take control. Why? Because the was completely out of your control. Someone you trusted most did you the worst. It is very, VERY hard to accept.
Go the the yellow box on the upper left and check out the Healing Library. There is a TON of useful info up there. Some of it is not going to make sense right now, you hurt to much. Take it a little bit at a time.
You probably do not want to eat or sleep. Crying becomes like breathing was before and breathing has been like hard labor. You are exhausted and nothing helps the pain. I talk from very recent personal experience, I know how you feel. There are THOUSANDS of people here who know exactly how you feel. You need to focus on you and your children. If you are not hungry, eat a little bit. Drink water. If you can't sleep, just try to rest. Keep the house as stable as you can for the kids.
Lostgirl12 - All I can do you for from here, besides words, is pray. I am praying for YOU specifically right now.
"Casting all your anxieties on him, because he cares for you. " 1 Peter 5:7