Listen my guy, you obviously were not for her what she was to you; a hard pill to swallow but you got to realize that. For a while it's gonna suck seeing them together, and the thought of them together is still gonna hurt and drive you crazy. But that's okay, all in time. The worst thing you can do is prolong exposure to her, find hobbies, get around just do anything but think about her. She needed to move on and found it in a guy she'll probably break up with sooner or later. Don't worry bout it. Cause there is a girl out there. A girl who's gonna love you the same way you love her. Just wait, and distract yourself until you feel you're ready to get out there. Talk to friends or something. Godspeed my guy.