Have you had an MRI of your lower back. Imaging is an important diagnostic tool. Not the only one mind you. For years I had lower back pain: I must have done PT 5 times. If it is sciatica related PT will help. There are certain modalities that really help with that issue such as the Mckenzie method. I also did spinal decompression and that did nothing. Finally, I went to see a myofascial release specialist who was also a trained PT. Guess what? I had super tight Ileo psoas muscles on both sides. He released the tension in both of those and there went 10 years of pain. So never give up and remember, just because you don't see on an MRI doesn't mean you are making all this fuss for nothing. And if you know nothing about the Ileo Psoas you are not alone. But thousands of people have it because we sit all the time to do anything. Our ancestors who had to walk 10 km a day to survive did not have problems with this muscle. But if it gets tight your back will pay the price.