[stygianwitch]

No you're not bad for thinking like this and you clearly do feel bad about it but you can't keep doing everything for them, with their health being as bad as it sounds they are only going to become more dependent the longer this goes on.

Vodstok and Novakru both have good suggestions that could help. I don't know how it works in the States but you could try finding out what kind of help would be available to them in their financial state, if there is free help available arrange for them to get it, it may be time consuming to begin with but it will take the burden off your shoulders.

Also, explain to them that your family comes first but you will help them (if you're happy to do so) where it falls in with your regular routine, for example, get their groceries when you get yours , but that you can't be at their beck and call 24/7