That's pretty amazing... Two neg. x-rays and your feeling kicks. I always feel kicks from my mamma's when they are Prego's. it's usually about 7weeks in. While they are sitting right at my side in the chair with me. It's the coolest thing in the world other than my own pregnancies.
Will this be your first litter?
Are you at all prepared for this if she is?
I would set up the whelping box. If she is pregnant she should start nesting. But most importantly if you have any inkling that she is, get ready NOW ! You don't have much time. It is better to be prepared for a false pregnancy than not at all. You need to take her temp. starting now. And than two to three time a day for the next week. If she is pregnant her temp around 100 deg. Here is a link that may be of some help to you .
http://www.debbiejensen.com/temp_chart.html
I am in no way a pro at breeding and whelping pups, although I have done it with my own and asisted others. I would be glad to help you by answering any questions you have. But for the sake of your pet be prepared for an emergency trip to the vet.