Upset, angry, obsessing about him and OW

Today is a bad day. I need to vent, and I want answers. Everytime I look at my son, I get a painful reminder that his father married OW 6 weeks after break. Obsessing about how a man can just move on, leave his child, family, home, dogs, etc. I know he was and N, isn't normal,but for 7 years I tried everything possible.
I can't help but start to blame myself. Why today? My mom and ex's mom were really good friends. They just got back from a 2 week cruise with friends, and my mom is still upset. She is planning on stopping that friendship, and I don't blame her. Ex's mom has nothing to say about her son. No emotions, nothing. I think she has a problem to, because I know if I was trying to open up to one of my friends, they would have some emotions about this whole messed up situation. Every time my mom tried to talk to her, ex's mom just sat there.
I have anxiety today, anger, and I am sad. I realize that he stayed with me out of convenience. Then after the break blamed me for everything. Blames me for ruining our finances, blames me for ruining everything I touch. How do you get over someone you have a son with, and "had" a life with. I am so scared of starting over. I am 37.
His wife is 13 years younger than him, married to the man that I thought I was going to spend the rest of my life with. Who does that? Why???