How could his feelings change in 2 nights?
They didn't change in two nights, freebyrd. They changed two months ago when you had a fight. He's been just working up to actually ending it.
That doesn't necessarily mean that he was cheating or lying about working either (although it could mean that) but even if that were the truth and not just a guess, it doesn't matter now. What matters is that you, as quickly as possible, get to accepting that he's gone. That will help you to go through the other 5 stages of grief you'll be going through that will eventually get you to the blissful stage of indifference to him.
Go zero contact now. Do your crying and moping about for a short while and then push yourself to do things that will keep you busy with friends that will help you to keep your mind off of him. Thats what you should concentrate on now... not why or guesses from us as to why.
Breakups happen. People get through the honeymoon stage and start to realize that who they are with just isn't who they want to continue to stay with it can be that simple and you accepting that is all it is will help you get through it quicker.
P.S. Why does your thread heading have the question "Getting back together" in it. There is no indication that that is even a possibility? Don't hold onto that hope. It will make you stagnate in your pain even longer. He knows where to find you if he's going to come back but don't hold your breath. Get on with your life without him in it.
Last edited by Wakeup; 03-02-14 at 10:38 AM.
Reason: added
“The willingness to accept responsibility for one’s own life is the source from which self-respect springs.” ~Joan Didion