Help me, im miserable?

i got dumped, but no one but my gf (ex now) knows why. im so miserable, i think that today is a dream, a bad dream and that im goin to wake up, and when i see her we're still together. but obviously no matter how hard i hit my self to wake up, im still dumped and miserable. any help to how i should deal with this by either movin on, or tryin to get her back. i miss her