He cheated on you. That means he dated up when he was with you, because you have more class and courage than to do that to someone. You have more to offer a partner than he does, and you deserve someone who can offer you back in kind. In time you will come to see that.

Only thing you can do right now is let yourself feel your grief, cry, take a couple of days off, and treat yourself gently. Watch good movies (not romances), read, spend time with family and friends, engage yourself in your hobbies, and keep your mind active. Do some involving puzzles (sudoku, crosswords, maybe an adventure game on your computer) that require you to focus and concentrate. Eat right, get good sleep, baby yourself a bit. You love YOU for a while.