I am actually surprised they did a xray at this stage. I have done ultrasound at 30 days once and you could see one bubble which they said could possibly maybe be one puppy. However at 50 days we did another xray and saw 3
. From what I understand the bones have not calcified at this stage, and thus would not show up. I could be wrong. However on Bridgets last litter 3 were born ( we skipped the ultrasound ) and in the Xray you only saw 2. So I would wait until she is closer to her due date and try again.
So yes she could be preggers!