Yes, it sounds like you probably don't have a good case since you aren't in therapy or trying to find work or haven't a lot of the time. Whether you "could" find work is not something considered; the problems of the economy are not considered when dealing with your, personal illness problems. But I would check with a lawyer; they would know for sure if you had a "case" and be able to help you most (as they'd have a financial stake in your getting it).

Didn't your family give you some income when you were taking care of your mother (so they didn't have to take care of her!) or consideration afterwards (if she died, leave you the house or most of any estate, that sort of thing)? If you have siblings, I think I'd swallow any pride and come up with a plan whereby if they didn't want to be "burdened" with you that they contribute some for your past services and help you find a job you could do or something.