I was just wondering how I can check how many litters a kc registered bitch has had

Go to your  MyKC account, chose Tools & resources, pick breed, type in the dog's name, then when the details come up click on the Progeny tab and all pups will be listed there.

If you haven't got an account you can pm me the name of the bitch in question, plus what breed she is and I'll check for you