I totally understand this feeling. It's like that with my family and was like that with my friends. I used to have a decent number of people whom I could rely on like that. It turns out that it was all very fickle and fragile. Thinking about it now -- it seems so fake. My family is even worse.

I don't know if you can do more than talk to them about it and try to make things on your own terms. Learn to say "no" and learn to be "busy" even if you're only laying about watching television. You don't seem like the kind of person who needs to feel like they're needed in order to be happy; you need to have the roles reciprocated. Quid Pro Quo I guess you could say.

Talk to them and try to make it change. If that doesn't work, you might have to settle with how things are or cut people from your lives. The latter, I can tell you from experience, is very lonely. I did that and while I regret it -- I only do that because lonely is a very scary place.

Don't you feel great while doing it?
If so, then you should be happy to the rest of your life, because you know they rely on you they need you, you're an important person in their life!

I used to think why should I care anymore while I give and don't get anything in return? Till one day I realized that what I get in return was satisfaction and the great feeling of making a difference in their lives.

Don't over do things, just limit your self with what you can do, your terms now.

Stand up, be seen and be happy.
and remember "It's a great satisfaction knowing that for a brief point in time you made a difference."