All Medical People I Have Seen Tell Me My Problem

All medical people I have seen tell me my problem is not medically diagnosable but they can tell exactly what my back is doing, show me on a skeleton model an show me on xrays where it is probably occurring. But they can't get a picture of it. My spine pops in two places causing extreme pain that shoots down my left leg and into my foot. I'm usually down 2 to 3 days can't predict what will make it do it. Any ideas????