You can validate his feelings without agreeing with them. He may feel as if he doesn't love you "enough", but that doesn't mean you feel the same way about him.
Marriages have rocky times; sometimes you don't feel like you love each other, or that the little things keep getting in the way. Marriages that can learn to cope with those times will be stronger and go the distance.
Have you discussed marriage counseling recently? What's going on with his late-night coming and going? The last I saw, it sounded like he was doing some serious cake-eating.
Me: 44, Wife: 39 M: 17 years T: 20 years Bomb on 08/25/09 1/13/10: MC started 1/28/10, 2/8/10: More bombs 8/28/10: Wife moved out No talk of D, no movement