Well, my reply might get long!! I'll just tell you my story - so far ...
During training for my second half marathon last year my low back pain was getting significantly worse. I have scoliosis, so back pain is not entirely new but it was getting ridiculous. A very tight feeling across my lower back that I would try to stretch out by doing forward bends. Then my left hip started hurting - more stretching - then my left glute started hurting. Then I developed this terribly sore area on the left of my lower lumbar. I was seeing my chiropractor constantly. I had started HC assuming that strengthening my core was the obvious solution. Then I started seeing a massage therapist who did deep tissue massage to find relief. She really wanted me to start yoga. Started adding Yoga Relax 2 - 3 times/week. Between the yoga, HC, massage I was finally getting some relief. Then in the fall it just got bad again. So I stopped running. Didn't help. Finally broke down and saw a sport ortho. doc in December. Xrays showed nothing, but he referred me for PT. I went to my the PT I've seen on and off for years for other issues - he's excellent. During my first eval - which took a full hour, lots of measurements and questions - he fully believed I had a torn disc in my back. Basically with the tear the jelly-like fluid in the middle was "leaking" out of the tear and affecting all of the surrounding tissue and nerves. And because of of the location of the tear all of that forward bending I was doing in yoga to try to stretch it out was actually aggravating the tear and forcing more fluid out. Which explains why, after a while, I would finish the yoga and feel like I had to do it again because my back felt so tight. Soooo....
.... I was instructed to discontinue yoga for now, absolutely no bending (which makes unloading the dishwashed and dealing with the dryer interesting), no impact and specific exercises to strengthen areas where they found weakness. Oh, and do back bends, or "cobra" as it's called in yoga ten times every 2 hours. Which of course felt like the opposite of what I should be doing. Oh, and visits to the PT 2x/week for massage, adjustments, e-stim on my tissue, then eventually exercises in the gym.
The first visit to the PT was in January. Finally in mid-April I was almost pain free except for what apparently was scar tissue in my back from the damage - which my massage therapist is now trying to break up. So, I stopped going to PT for the last three weeks, continued the exercises at home, then got a little cocky and started adding some running intervals in with my walking. And some HiiT. Then I spend the day gardening this week. Then the pain came back in my hip, back and glute so ended up back on Friday. They believe I opened up the tear again. Apparently it takes about a year (!!!!) for things to heal.
Basically I trust my PT more than the doctor. He's more thorough in his exam and more holistic in his approach to fixing the problem. I never had an MRI but the reading I did on his diagnosis matched my symptoms perfectly, and all of the stuff I've done to get better had (slowly) worked. Sorry this answer was so long, but I figured I had something to offer through experience. Good luck!
Jen