No definite diagnosis for pain, but Lyrica helps. Should I be concerned?

I had severe lower back pain and shooting pain down my legs for about 2-3  years. I am a healthy, fit, 31 year old woman.  For some time I could not walk without a cane.  I had MRIs that could not find a reason for the pain.  I had nerve conduction tests and many other tests that could not identify the problem.  I have some loss of sensation in my feet, up to about my calves.  I started Lyrica about a year and a half ago, and it has helped enormously.  Sometimes I have pain, but it is manageable  I have occasional shooting nerve pain, but that too is much better.  I recently had to cut way back on Lyrica for a few weeks because of finances.  At that time, the pain returned.  Now, I am back on a higher dose with positive results.

My only concern is that I never had a clear diagnosis for the pain, loss of sensation, etc.  So is the Lyrica just masking a problem that I should be concerned about, or could it be healing an unidentified problem? 

Thank you