I am sorry for your pain and I hope the operation goes well. I can't say I know the difficulty of having to choose between painkillers and rent. That just sounds awful. I haven't seen Sicko yet because it hasn't opened here - but I live in Australia where we still mostly have socialised health care. Our evil right wing government keeps trying to make it harder to access but I still know that if I were sick I would not have to choose between painkillers and rent. I am happy that you have the union to help look after you, and you will be able to continue to get benefits and not be fired.
I know you won't feel better in the near future but I am sure you will in the long run.
Good Luck.