My family won't stop smoking in the house

I'm so done. They know my condition, they know smoking, even passive, makes it worse, but they just don't give a shit, and sometimes try to gaslight me as "it's not that big of a deal."

The thing is, I can't move out, I don't make the money and probably wouldn't even find a flat in the first place. My boyfriend has a house, but he lives in one room and rents the flat to his father, and I don't feel comfortable using his father's flat.

Currently I have to cook and shower at my parent's and I spend as little time there as possible. But they're also all so full of problems they're not willing to solve and it's apperant that they aren't willing to make a small adjustment in their life for me. They're causing me so much unnecessary stress and pain. I'm always glad and willing to help and listen, but I get this in return?!

I just don't even want to see them anymore. I feel so sad and guilty, but at the moment I wish I could just not see them for a while. I want to stop contact until they realize what they lose by just not stopping to smoke inside, but I also know they're too selfish to change. If they at least stopped until I'm able to move out, but no.