Acute pain under my left buttocks. Me?

All of a sudden one day i got a pain in my left leg under my buttocks. I consulted two general physician thinking it's a muscle catch. After three weeks, seeing no results. I consulted a orthopaedic. He did few checks and suggested to take medicines and injection saying it was a Normal muscle tear. Even after two weeks of taking medicines nothing changed. Later he advised for a MRI scan. Seeing results he said everything is normal and continue with medicines it will reduce, but it didn't. So I went for ayurvedic treatment , pain reduced gradually. Now it's back again. I don't feel the pain while walking sleeping or even riding bike. But when I try to suddenly shift my leg posture while sleeping I experience it. Please help me whom to consult. I don't even know what's the cause of it. The mri result said Mild bilateral sacrolittis (left > right) Whom should I contact in Bangalore to get what is happened to me? Please help