I am so sorry you are in this situation... I feel for you totally.
If you can move on and move past him (great advice - I give it but have trouble taking it myself).
It's a long lonely road to travel but remember that there are people here at PC that are ALWAYS listening and giving you brilliant advice.
If he has moved on so quickly.. imo.. it wont work out and he wont be happy but don't hold hope for that (been there done that - it's not good for your state of mind).
Hugs to you oooxxxooo