Thanks to everybody for the responses. It helps a lot to hear from other people who have gone through the same thing. I'm a bit tired of hearing that I don't have anything to be depressed about and I should "snap out of it already" and "count your blessings." If you haven't experienced Depression yourself it's really hard to understand.
I see that a large part of this has to be lack of exercise. Much as I've resisted the whole idea I'm going to have to consciously look for ways to build in more activity into my day. Plus a small amount of actual EXERCISE. I used to say half jokingly that I didn't want to do anything that might cause me to break a nail or break a sweat. Guess that's not working so well for me any more.
So thanks for the caring and all the suggestions, it really helps and I feel better!