It just seems to me that you are staying with him because you are afraid of not being with him. Paradoxically, you won't be able to figure out how to survive without it until you can learn to survive without it. "It" being whatever it is that he is unwittingly providing to you in this relationship.
At this point, he just wants out but doesn't want a sticky mess on his hands. Honestly, you would be doing both of you a favor by doing the dirty work yourself - its an act of courage but you need to keep a stiff upper lip and make a decision not to put your emotional fate in the hands of someone who hasn't put his emotional destiny in yours. Set yourself free. If you don't do it now, he's gonna fall for someone that rings his bell and he'll do it for you. Better for you to what needs to be done before its done unto you. Trust me on that.
But, all the clinical bullshit aside, just be good to yourself and gear up for the difficult task ahead. One thing that might help to think about is that the rest of your life is NOT going to suck. When in love, it seems like the other person has the keys to your happiness. They don't and the feeling that they do will pass eventually.
Next time you pass by a bookstore, have a look at this book as well as other writings by Leo Buscaglia.
