Hi Granda Deb
I am so sorry you are suffering with that staff infection in bone, it must be really hard for you, and back pain on top on that. 
Go ahead and tell them you'd rather be working than home for illness. Tell them you don't feel very lucky, but you know you are blessed in having your loving family, that you are very grateful for, but still, you often feel lonely and depressed being at home and in pain.
I do believe some people who have not experienced long term problems, don't always realize saying those kind of things hits a nerve with a some of people. Especially on a bad pain day. I think they are often are trying to take a light hearted attitude towards the situation you are in, to make you feel better.
Do you know what I mean?
Hope today will be a low pain day for you Deb.