BF - taking care of someone can take it's toll on anyone. It isn't easy, I know, I have my mom. I can't even get away, since she lives with me.
BUT, as I have told her, I CANNOT TAKE CARE OF YOU, IF I DON'T TAKE CARE OF MYSELF.
I have to say NO also. You are doing all you can, and you need a break now and then.
Sometimes they do take advantage of you, because they are so used to you doing it FOR THEM, they then won't take of things they are able to, since they have someone to do it for them. It's not easy, and I feel for you.
Hang in there, do what you feel is best. Your doing the right thing. I should listen to my own advice. LOL
Lots of Hugs, Nikko