Selfishness and uncertainty

I am tired. I am worn out physically and mentally from caring for my Mom. She is at a stable point, but nowhere near well. I am most tired of the uncertainty cancer brings. It is uncertain on a daily basis whether she is getting better or getting worse. She is nearing day 17 and is waiting to lose her hair again(she lost it the first round of chemo, but not the second). They are using the same chemo's that were used the first round.
This will seem somewhat selfish, but I am tired of being asked "How's your Mom?". It is a daily and well meaning question. I know it is asked out of love, but every time I hear it I want to scream! I want to say "She is either living or dying. I have no idea!", but instead I do my best to answer. The truth is, I have no idea!! She is not the person she was 2 months ago, but maybe she can be this way a long time??? Again, I have no idea?!?!
It is hard being a patient mom and caretaker!