Backache, muscle contract. To visit.

I have backache from 8yrs and then some unknown pain started in my left thigh part near to knee area. Some doctors told it's due to nerve pressure in spinal cord so pain is coming in leg . I thought it's bone or muscle pain. I took MRI scan for thigh part twice but they told it's normal. And that leg pain is coming in right thigh also . I can't sit on floor, if I sit I can't get up. The pain feels like some thunder appears in sky during storms. It comes like shock wave. Suddenly comes stays n disappear. My left thigh is becoming very thin compared to right thigh. I'm so scared n worried about my condition. I went to orthopedic doctor he told due to lack of exercise pain is coming. I used lot lot medicines pain killers but none if doctors given me permanent solution. I have nerves weakness, hands shivering it be so cold when im tensed. Masturbation is one of my weakness from 16yrs. All my health spoiled . Pls suggest to which doctor I have to visit.