I felt exacly like you. The pain is simply overwelming at first, the confusion...It's like an upside down world. Everything we knew was wrong, and we did nothing to deserve that.
What can I say to ease your pain? It does get better. Being in love with a cheater is one of the most painfull things we can go through because it not only undermines our notion of self worth but also our hability to trust our judgment of people. I myself am struggling really hard to trust again. Not only people, but specially the way I analyse things. You should cut her off now. Think of her as a limb you had to amputate in order to survive. Focus on surviving, on learning how to survive without that limb. The rest will come to it's place, but it will take time. You are a good, decent human being and you wll have another shot at finding someone that not only loves you but deserves the love you have to give. You cannot believe these words for now, but have faith that although it hurts like hell, she is a limb you have to learn to live without, and life will be easier as it goes along. You will look at this moment in your life as the beginning of your liberation, in order to go where you where supposed to be.