Pain particularly on chest and back.

For many yrs my mother has asthma, and she suffers from lots of pain on the middle of the chest, back, lower back and on knees(PAIN IS ON CHEST, BACK, BACK OF NECK, LOWER BACK, KNEES) Few years back we consulted with an asthma specialist, and she got treated with it. She has got lots of relief from asthma but she is still suffering from the pain. Whenever she does some household activities , she again suffers from the same pain. For many years we have consulted many doctors but none of them could figure out the actual reason behind the pain, some of them would say gastritis, some would give anxiety pills and all, but she still haven't recovered from it. I want to know that what kind of disease she could have and which specialist we should consult. PLEASE GIVE SOME GENUINE TIPS REGARDING THE SAME.