Dear Anna, there will be Christian voices that will say you need to stay with Josh. They will tell you that you should forgive him. But Anna, you don't have to stay to forgive. I can't tell you what you should or shouldn't do, but I can tell you, and every woman in your situation, that you have choices.
Life is about learning the lesson of who you are and who the people around you are... But ultimately how you answer those questions depends on who you believe God to be. If you believe God to be the Great Judger, that has an effect on how you treat other people. And yourself. But when you start to see God as the Great Lover, the world changes.