FrostEntropy, you will not be able to get rid of that pain in a very, very long time. There is no cutting it off. My girlfriend emotionally cheated on me and two years later while the pain and paranoia are gone, I don't think I will ever be able to forgive her. Every time I see a guy with the same phenotype as the person she had this affair with, I unfairly want to smash his face into the wall.
Your friendship and relationship are over. Mine was salvageable but yours is not. There is no screaming at your friend that she is a lying slut becaue guess what? He knows. He slept with her and he knew she was with you. Actions speak louder than words. Your "break" is for her to figure out which one of you she wants to be with; that's the short of it. You need to cut her off before she tells you her decision. You need to think of the future instead of just the now. You say you want to heal, then let the pain stay and cut her out of your life. Every day the pain will hurt a little bit less, I swear to you. I know it hurts and I know that feeling well but it will dampen as time goes on.
You will lay in bed for hours and cry, that is normal. However you need to take this time to focus on you. You don't sound like you are happy with yourself, mate. The tone of your post makes it seem like you have low self-esteem. Take this time and go to the gym, trust me it helps the pain. In the process and through the pain you will become better. Your self-esteem will get higher and higher and how you feel physically will effect how you feel mentally. Go out and try new hobbies and meet new people. I know you will want to be alone for most of this process but getting out helps because it shows you what fucking awesome things you are missing and how you are better off that you got rid of someone who doesn't respect you. That THEY DO NOT DICTATE YOUR HAPPINESS. They may effect it but they do not make you happy, you make you happy. You choose to let the good in as well as the bad. Cut the bad out. Your ex is not the loving and respectful person you think in your head.