A little frustrated

I'm a little frustrated/worn out right now. Since about 2006, I have been a sounding board for my Mom. It started with my the process of my grandfather moving into the apartment at my parents house. First it was the stress of an independent 80+ man figuring out how to live in a new place basically with his child. Then it was the issues around diagnosing his ALS and following treatment, hospice care, and death in 2007. Since then it's been one thing after another... we'll go weeks without anything, then we'll have weeks where there is something everyday.

I know she needs someone to talk to and I don't mind being there for her. But, sometimes it feels like I am being taken advantage of. When she calls, she asks what I'm doing, but it doesn't matter if I am busy or not - she just keeps going. I don't know what to do.