Tam-
So many good suggestions, and I think most of the ones that center around basically taking care of yourself in the diet, sleep and chemistry realms are close to the matter. Only you by trial and error and much patience can arrive at the right combination.
Girl, you are NOT old!
I understand you are not up to much physical exercise, but I would add my recommendation that you at least spend some time out of doors. Even if you need someone to tottle you out to the front porch to sit for a while -- something magical happens outside (and I don't know where you live, but I have lived in a big city and it works even there -- better than staying inside). And going back and forth to work or the doctor does NOT count.
And above all as so many have told you, don't feel guilty about it.
-Glenn