Actually - okay, so my fiance and I have been together for 5 years this July. And right around the 4 year mark, which is where you said you are, I felt the SAME EXACT WAY. Depressed, felt like I wanted to leave him, I even bought a book called, "If This is Love, Why am I Unhappy" which I never read and wish I didn't waste my money on. Anyways, back to the point, it's weird that you and I felt the same way at the same point in the relationship. I got over it, it lasted for a couple of months, and I don't know why it happened - but now I'm back to being madly in love for the past like couple of months and because of all we've been through I value our commitment and decided to marry him - well, not yet, but eventually.