So much good advice here HappyBumblebee. You have every right to feel upset, angry, fed up, and despondent given you have so much to cope with.
My tuppence worth would be, perhaps look for any tiny bit of happiness or positivity, like, as you mentioned, enjoying the birds in your garden.
I can completely understand you not wanting to burden or worry your family with all your conditions. I really empathise. From my own experience, knowing a loved one was suffering dreadful illness really clouded my whole existence. I forced a happy disposition, a cheery, positive demeanour and the strain of wearing a mask was terrible. I don't let my children in regarding my various ailments - none as difficult and severe as yours. They are adults and we are close, so I don't want to blight their lives in any way.
There will be outlets other than family however, where you can talk, share your worries, your feelings. I do hope someone can point you in the right direction for that sort of therapy. Having someone to share your worries and listen to your concerns would be helpful, I'm sure.
Do of course let off steam here. So many Grans are wise, supportive and compassionate.
Keep looking for those tiny bits of silver linings and recognising them...they can ease the worries and fear of a day slightly.
As Churchill famously said " Keep buggering on " KBO.
Sending you hugs.