Pamela, are you engaging in some kind of organized physical exercise on a regular basis?
Also, is it possible for you to take a class in something you enjoy ~ photography or painting, maybe?
When our difficult children become our primary focuses, our spirits suffer.
That is what I say, anyway.
We become depressed because, despite all the energy devoted to the difficult child, the situation does not resolve. There is always some other crisis brewing, and we begin to lose faith with ourselves, with our own sense of efficacy in the world. That is where learning a new skill comes in. Whether you choose dance or golf or photography, learning a new skill will often return a sense of control, of challenge well met and accomplishment to your life that will better enable you to survive the emotional battering life with a difficult child brings. (I picked ballet and then, karate? But you could do line dancing or belly dancing or ballroom dancing or Tai Chi or yoga, and the good effects would be the same.)
I think so many of us suffer from situational depression. (Only the "situation" never resolves!) Because the difficult child is not going to change, we need to change our own patterns, and make self nurturing a priority.
We have to learn how to open new facets of self in areas that have nothing to do with the difficult child.
I am sorry this is happening to you (and I feel even worse that it is happening to me (winks).
I hope you feel stronger soon.
Barbara