granny I so feel for you. You are lovely for doing what you do but honestly you should at the very, very least get paid 'expenses'!
My own mum, when I got married, laid it on the line for me. She told me in no uncertain terms that she was never going to be cm for my kids if I ever had them. She'd be the best gm ever, and she'd love them and see them but as for being permanent cm, she wanted no part of it, paid or not.
I was shocked! Really aghast! Here my soft spoken mum was telling me this - I at that point thought I was unable to have children! I was really offended!
Fast forward (sadly mum has passed) 13 years, we have our own ds (that I WAS able to have) whom I love dearly. I've Already told him I'm not cm for him! Like I said, unless it was that or children would be in the street, I'm not interested on a permanent basis either at all! Not cm doesn't mean you wouldn't love them.
Anyway, granny, I'm sorry this is how you are being treated.