There' only so many things, "we" as a forum community, can say without sounding repetitive. This guy left you to go chasing the past. You can't do anything about that but respect the fact that he didn't cheat on you and had enough decency to leave you. Now have some self respect... cry and feel the pain but don't let it defeat you. Don't be a fool.
It's time to pick up where you left off before you met him. Rely on your good friends to lift your spirits. Find a hobby, go out and have fun.