I would be really impressed if you can truly move on from that fact. That is, if Im understanding you right and he cheated on you? Because that is incredibly difficult to forget. The key thing to any relationship is trust, and its really difficult to trust someone again when they've let you down like that...But if you decided to separate and he got together with someone else, thats a different story. If you two really wanted it to work, the only thing I can suggest is sit down together, and write a list each, of things you would like to change in your relationship. Work out the areas that truly make a difference, and give yourselves a set time. Like if in two months, things are still making you unhappy, agree to part. That might sound a bit silly, but thats how my boyfriend and I worked things out, and we're now happily living together. I really hope it works out for you - best of luck to you both! :)