I can tend toward the lazy re: housework and picking up, too, but like you I much prefer a neat environment around me. It DOES help me feel less depressed, so maybe it will help you too. It's so hard to interpret why he brought this up- you're right, from what I know it's completely out of character for him to say something like this. Personally, I'm becoming rather suspicious of any odd behavior so I would probably just try not to give it any more thought other than what you've already concluded, which is that it would make YOU feel better to keep more on top of it. I find doing just a little a few times a day is easier than hours at a time--
When the men on the chessboard Get up and tell you where to go; And you've just had some kind of mushroom And your mind is moving slow; Go ask Alice... I think she'll know.
