Where has my stamina gone?

I used to bake two days a week, do the daily mountain of washing, cleaning, shopping, ironing, playing and feeding, then help with the homework before finally washing up the evening meal dishes and getting all four daughters washed and into bed. For many years it seemed that I was either pregnant, breastfeeding or pushing prams and pushchairs up and down the steep hills of Plymouth. I weighed just under 9 stone, was never fat, always sunkissed from being in the garden, by the beach or in parks with the girls. I ate well, slept well and the days whizzed by.

Now, having seen lots of old photos, I wonder where my stamina has gone as I recover from another half-term of child minding. I am exhausted and have caught yet another virus and will be seeing the Doc in an hour. I need an injection of stamina... any suggestions?