Help Please My Dog May Be Sick?

I think the main problem was that you switched their foods. Dogs can't have their foods switched immediately, it has to be gradual. Also, Purina is not a good brand. I would suggest something natural if your dog is fragile, maybe Natural Balance, Innova, Artemis, etc. would be better and healthier. I would switch back to the old food and slowly switch the food. If the dog is having a hard time peeing, they may have a urinary tract infection, or her urine crystals are bothering her again. I would go see the vet. If she's not drinking, try maybe something else that has liquid, maybe ice? Anyways, I would at least call the vet and ask instead of paying a visit if you don't have enough money.