Hi, it sounds like you're under a lot of pressure and perhaps not getting the opportunity to say everything you're feeling and be heard? But remember you do matter in all of this.
I'd say that you really need a break/s in all of this. Doing what you're doing can be SO hard going. I'm guessing you feel a real sense of responsibility for your grandparents but sometimes things can come to a point where you just have to stand up and say "I can't", "I won't" to some things. Doing that is NOT a weakness on your part!!
It won't mean you love them any the less, but you really have to protect yourself in all of this for both YOU and them. You can still be there for them in other "smaller" ways in caring for them, but it sounds like this is way too much for you and even taking away from the relationships you could be having with your grandparents.
SO you really need to contact someone.......members of your family?............Social services?.............the hospital?............the doctor?..........whoever is involved............anyone (!) and find some sort of "middle ground" in what you're doing for them.
And get some support/advise/understanding from other people caring for members of their family too- there's a forum for caregivers support on here and there'll be others out there too, really make use of them.
But the depression- I'd say you're losing a lot of real focus on yourself with the situation as it is, maybe really think about yourself and your needs a lot more??
And perhaps think about the things that might help you personally whether that's having more time going out doing things, more time to relax, exercise, diet, doing things you enjoy, finding an interest........But I'd always say talking/sharing can help a lot as well.
Oh, and make sure you're putting the right amount of pressure on your doctor for him/her to help you as much as possible with your pain relief!!
Here if you want to talk........
Alison