What to do when parents keep telling you to think about them and you do, but they don't seem to understand you?

My mum has recently been giving me many talks about how her health is deteriorating because of me. I feel bad and all, I really do, but they don't seem to pick it up. I tell her I would like to live my own life, and that she could stop stressing about me all the time, but she is against that idea. It doesn't seem like she really understands how I feel, and I'm not sure how to tell her everything, because she is quite touchy, so her mood can change very suddenly. thanks to any people who replied/replies in advance(: x.