Unique situation~ need advice?

My husband of 5 years left me 3 weeks ago today. (He's 33, I'm 29). Says he "wasn't happy" and that he "shouildn't have to work so hard at marriage" and asked me to decide on what I wanted (house,items,etc.).We are finanically stable,have a lot of ets and no kids. We have a great marriage, enjoy all the same interests and rarely argue. He says he still loves me, but "wants to be happy" that "life is too short". When I told him that the gr isn't greener on the other side, he says he's "off for greener pastures". There was no blow up and he says there is no other woman. I am thinking midlife crisis? Our 5 year anniversary is at the end of March and he has planned a trip to visit a buddy. I told him that wouldn't be right if he was gone and he said,"I'm trying to move on, making anniversary plans wouldn't be helpful". Yet he admits to listening to depressing sad songs and even has "Best I Ever Had" by Gary Allan on his myspace page.I am not sure why he is so hateful.Insight please?