RA has to be somewhat advanced in order to show up on x-rays, as x-rays show only bones, there has to be damage caused to the joint in order to see it. To read more about x-rays, check out this article diagnoses of RA - the section on imaging techniques like x-rays is on page 2.
don't rely just on an x-ray. I had x-rays 5 years ago, which did not show any bone damage. After worsening symptoms I had an MRI which is supposed to show any soft tissue damage which did not show anything. After 5 years of worsening pain and a new rheumatologist, who ordered an MRI with contrast, the ra is now advanced. So if the xray doesn't show anything and your symptoms persist or worsen keep pushing for answers.