I'm probably the wrong person to address this point because I didn't take on the full time caring for anything other than relatively short periods of time. Oh I did the admin, worried myself sick, logged scores of thousands of miles backwards and forwards across the pond, but always knew I would be returning home at some point. So I never had the trapped feeling that I think is so common. My point, if I have one, is that words are cheap. You may not like what you are doing, you may not like the person you are doing it for, you may not even like yourself, but the fact of the matter is, you ARE doing it, and for that very reason you should try not to get so down on yourself. You may not be able to continue to do it day in and day out indefinitely, but you are doing in now, and that earns a great deal of kudos from me at any rate.
Another thing I should perhaps mention: there is no shame (although there's always guilt) in admitting that this is not the correct role for you. This is your mother, correct? Depending on your prior relationship with her, what I'm going to say now may not ring true, but would she really expect you devote the rest of your life to caring for her? Now some parents would, but I know I wouldn't want my children to do that for me. My own mother would sometimes ask me in a worried tone "You do have a life other than this don't you" and when I reassured her that yes, I had a home and family, she would say "Thank goodness, I wouldn't want to think that this is all there was for you".