OP I really feel for you.I am the same age as you and help out with DGD who is 2 at least twice a week.She does go to nursery ,fortunately between them they can afford the fees but as DD is a nurse,and her partner commutes and is out 12 hours per working day I have to set my alarm for 5.45 am to be at their house to take over,and then back again at teatime to collect and do bedtime.But over the last year since she's returned to work I've found it increasingly tiring.And I'm not suffering with fibromyalgia.I did however have a really bad bout of chronic fatigue years ago post virally,and know if I get run down I can have a sort of flare up.Plus I still work part time at a physical job,and have a 96 year old frail mum nearby to help -she won't accept any outside help .Another thread !
However such early starts take their toll,and DD is now pregnant again.Added to which when she gets tired,which is often ,she has been very snappy and rude .I've posted a separate thread on that.
So recently I told her I was only prepared to do one very early start.And DGD comes to stay the night before the other one,or her partner has to go in later if possible.And I have warned her that I can't commit to do more than I already do when no 2 comes along.My DH is brilliant but has degenerative arthritis,and when we retire we want more time for days out and short breaks.We have worked blooming hard for 40 plus years,plus raised 3 children of our own,plus been a lot more sensible with money than they seem to be.
We absolutely adore our DGD,and feel privileged to see her so often and live so close.But we deserve a balance and time to relax,and so do you.