Why Is Cali Doing this?

Today I caught Cali urinating on the carpet! she hasn't done that since she was a kitten. Why is she doing it now? Is it because shes pregnant? I just cleaned the litterbox out this morning. I can tell that this isn't the first time shes done it this week. I was wondering where the urine smell was coming from and was thinking it was just the litterbox so Ive been cleaning it every day but now I see its my carpet! Anyone have any Ideas why shes doing this? and what can I do to stop it? oh and I do tell her no and bad kitty and put her in her box where she immediatly goes potty,

Ok a couple of minutes after I wrote that first part:
SHE JUST DID IT AGIAN! Right after she went in her box! I saw her go on my floor! IN THE SAME SPOT! she sniffed around scratched a little bit and squatted I hurried up and grabbed her and took her to her box again. WHAT IS WRONG WITH HER?

My girl is DOING THE SAME THING! We had to throw the rug away, and we can't leave anything on the floor or it's toast. Mu husband and I have chalked it up to hormones, but if she is doing it after the babies are weaned, then she will have to spend some time outside (after she is spayed).