I think something wrong with my cat?

my cat gave birth to 5 kittens 7 weeks ago. I. Have been taking care of her and her kittens very well, the kittens are all pretty healthy...but my cat is acting so odd =( she's hasn't been herself in a few days. She cuddles with me, but then she tries to bite me. She's been atacking her kittens too. Shes not herself, because she has never scratched me or tried to bite me like that. She cuddles first, then she tries to bite me or scratch me. And she's forgets to use the litter box sometimes and pees on our carpet. I'm not happy with her right now, she's never acted this way before =( What could be wring with her..??