Hi I can't speak as the person suffering with cancer, only as the wife of one. Suffering may be too extreme a word.
How do you physically feel? I know husband feels OK. He gets a bit sweaty for a minute or two, and that's it.
You seem to be describing a lack of concentration to carry out everyday tasks, which sounds like a stress reaction. Perhaps chat this through with your GP.
If I feel a bit overwhelmed, I'll tell myself, just tackle one task, and then have a reward: a coffee, a walk, or anything you like.
I had a very odd thought the other day.
Life is like a beautiful plait of hair, long and lustrous. The cancer is just a thin thread woven into it. You know its there, but it might not be too noticeable. The plait is still beautiful. It's just coming through every so often, like appointments, tests, or PSAs.