That is really hard. It sucks to feel betrayed and it really sucks to have it in your face. Give yourself a break. You are entitled to your emotions. I went through a really fast divorce too after finding out he cheated on me. While good in some ways, the shock of it is ... well, shocking. Give yourself time to grieve.
I know it is so much easier said than done, but you have to train your mind to stop spinning around him. When my mind starts working on the fact that he is still with her ... living with her and presumably having a grand old time ... I picture a door in my head and literally picture shutting the door on those thoughts. Doesn't always work, but I am getting better with practice.