cat pooping and peeing everywhere

I got a cat about two months ago from the Humane Society. Unexpectidly it had kittens...they are about 5 weeks old now. Recently, for no apparent reason our cat has stopped using the litter box and has decided to poo and pee on the carpet and at the front door (which is no where near the litter box). We've been cleaning the box out everyday but she doesn't seem to care. What do we do? Is it a matter of mental health or physical?

So the Humane Society didn't spay her? Or have a contract with you to get her spayed?
Sounds like she needs a vet visit! Going outside the box is not normal for a cat! Could be mental or physical.

Do you only have the one litter box? And are the kittens litter trained? If so, you need at least one more litter box....one per cat really helps. This is only AFTER you take her to see the vet!!!!