could be something called transitional lumbosacral junction. Not that uncommon either. I have it and no problem with movement in my spine, but have had 2 spine surgeries for spinal stenosis.
What you need is a full evaluation by a spinal surgeon, either and orthopedic surgeon who specializes in spines or a neurosurgeon that specializes in spines.
Once you have had a full evaluation, and an MRI, the spinal surgeon can than provide you with the answers you need. What is the cause of your spinal pain, what kind of treatments are best to relieve your pain etc.
X-rays will not provide the information needed to evaluate your spine and what is causing it. X-rays only show bones, you need to have an MRI that will show if there is nerve compression and what the causes may be etc.
Good luck
Fran