My cat had her kittens too early and...?

Please take her to the vet in the morning. She should be spayed as soon as she is healthy enough. I know that you care for your pet and she doesn't need to contribute to the overpopulation. Maybe it is b/c she is a little old for kittens now, but her health does seem compromised. Go to the vet. Good luck and I'm sorry about your cat.