If she had a big litter, it is possible that she is suffering from "milk fever" which is due to low blood calcium caused by moving calcium from her muscles and bloodstream into the milk.
Your dog needs to be seen by a vet RIGHT NOW to have treatment. Left untreated, your mother dog could die. THIS IS AN EMERGENCY.
The good thing is that treatment is fairly easy with an injection of calcium. Supplementing the dog with good quality, high calicum food like puppy food, and feeding calcium supplements will prevent the condition from recurring. But she needs the immediate vet treatment now.
Good luck with your dog!
Dr. Tanis!
Dog Veterinarian
10 years experience in small animal emergency medicine