The only sure way to know is if you take her to the vet and let them give only one x-ray. I don't suggest x-rays but I've had to have 2 of my cats x-rayed as we didn't know if there was a problem. Just sit tight and keep you vet on alert for the arrivals.
Griffin, try and keep everything in one post. You will get many more responses that way.
As for the food. Any cat should be on a good quality diet every day. If a cat is pregnant they should be eating kitten food and canned kitten food if they tolerate it well.
The queening box should be at least 3ft by 2ft for a small cat. A lot of breeders I know buy a tokeo cage for moms and thier kittens. You just want to make sure mom can get in and out and the kittens cant scoot off somewhere.