Heartbreak and darkness an end of a marriage...

So it's been awhile since I last posted. Things in my life have taken a dramatic change. My husband of 12 years, has fallen in love with another woman and I am trying to pick up the pieces of my broken heart and be happy for him. You see, it's my fault. I wasn't happy with a long history of addiction on his part, loneliness and feelings of abandonment on mine, I wanted..... I needed change. So in my brilliance I told him I just wanted to try and live as friends for now. It was my hope that as friends, we would once again see the things we once liked in each other and start getting along again. Also, keep our family together. He didn't agree and fought me tooth and nail. He was heartbroken and didn't understand. He cried for weeks. So finally last week, I decided to give him another chance. And he was happy again. Within 3 days, on my home from a day at the pool with the kids he calls me to tell me, hes going on a date. BAM! What!!??? Seriously? Ouch.
Yep, that's right. He has fallen in love with an old friend he met on facebook just this past week. My heart, to my surprise, shattered. I had to pull over the car on the side of the road, get out and throw up and cry. My poor children watched from the back seat in confusion. I called a friend to come talk me down enough for me to get home.
Its been 3 days since that day. He is so happy. Giddy even. And I am trying to be happy for him. I am trying to not break down completely. To not curl up in a corner and give into the heartbreak and darkness I feel inside. And it hurts. It hurts because I realize what I've lost. It hurts because I have never felt so alone in my life. He keeps telling me how great she is and how much I'm going to like her. He keeps telling me how the kids are going to like her. And I keep feeling more and more of whats left of my heart break off and disintegrate. Getting out of bed is my greatest challenge. Trying not to let the kids or him see me break down is my second daily challenge.

And where do I go from here? How do I go on from here? I know that the pain will eventually start to heal, but for now, it hurts so much I can't breathe. But I smile and quietly tell everyone, I'm ok and walk away before they see the truth in my eyes.