It sounds to me like you cat is pregnant and in labour! Try squeezing one of her teats and see if anything comes out. If something comes out that isn't a green colour then she is producing milk. If it is green, then she has an infection. I would guess that by now she has had kittens, if not, get her off to the vets as soon as you can, she could have a kitten stuck, and this is life threatening to both the mother and her kittens.
Please post to let us know what happened :)