I undertsand your pain.
I hope you are not in too much of pain.
Since every investigation thatched been subjected on you came out as normal and even then you didn't find a solution for it. If you're having any numbness, or pain radiating to legs or thighs, then you should do things like Surya namaskaras and back strengthening yoga. Maintain your erect posture where ever you sit. Sleep only in left lateral and upright position that is in supine position. This should help you.