((((((BIG HUGS TO YOU DEAR CYSTER!!!)))))
...and prayers, too!!!!
I am so sorry that you are going through all this. You are such a nice person and it just doesn't seem fair.
I want to encourage you that things will get better. I know we all hit these "down times" and they are a bear to deal with, but luckily they do eventually pass.
Here are some things that have helped me in the past during "down times"...
Maybe even taking a short little walk will spur you on to get back into exercising. Everything counts, even short walks.
And think about taking your meds. Break that down into a shorter span, too. Think of it. How many seconds does it take to open the bottle and wash 'em down with some water?

See, it makes it more manageable; it doesn't take much of your time at all and the benefits are long lasting. You can do this!
You sound like you love and care for your parents very much and that's good. But sometimes when I would feel overwhelmed by my parent's problems I realized that sometimes no matter what we say to them, they are going to do what they want to do no matter what. Sometimes it's best to stand back a bit before we get too overwhelmed by their problems and be rendered unable to help them at all.
Please, please take care of yourself. Even if it's small steps, it can be done. You can recapture your health and vitality. We are rooting for you and wish you much brighter days ahead!

Kathryn