I think this is more common than people think. My Krissy had six puppies and was taking calcium supplements and getting a cup of cottage cheese everyday but when the puppies were 5 weeks Krissy started shaking and collapsed.
She stayed over night at the vets and was no longer allowed to nurse the puppies. The vet said six was just to much of a drain on her. I dressed her to prevent nursing after she got home. THe puppies tried to get to her and she was very upset but it stopped after she dried up and they couldn't get milk.
My vet bill was over 1200.00.
If she were to have puppies again I would dress her after the puppies were 5 weeks old to prevent nursing. They can eat on their own then.
I know it was scary for you and expensive!