sounds like athritis i had it for 11 years doc sent me to pain clinic , i knew all along for 11 years it was osteoathritis , moved to wales and had hip replacement now waiting for the other one doing , but i am back in yoirkshire so i guess they will keep me waiting another 11 year , you can have this problem even in a young age i started when i was 25 year old , i wore a steele corset ,they said i was too young for an op , i had to wait until i was 70 were is the sense in letting some one suffer all those years , all the best to you
also could be syatica sonds like , does it go down your leg to your foot [ back of leg ]
Have you had a MRI done to your lumbar spine to make sure there are no degeneration of discs or spinal strenosis, and this is far fetched but even tethered cord? Xray will not show tissue and if you are pinching a nerve or your spinal canal is narrowing and pinching the cord you would see that on MRI.