I'll spare you the full story, but I've tried just about everything - Chiropractor, Osteopath, Yoga, Pilates, Exercise of all sorts, Physio (NHS in the UK), etc. Nothing has really helped - more paper the cracks than fix the wall.
Very little worked, and the pain has increased in frequency and intensity over the past 10 years or so - culminating in a prolapsed L4-L5 disc, and some nasty sciatic pain episodes around 7 years ago. The NHS treatment (pain killers and exercises) didn't help. I did all the exercises they gave me, and they did nothing. They discharged me without any improvement.
Three things HAVE really helped. Firstly, learning Alexander Technique  which got rid of the sciatica (and the need for daily pain killers) in a couple of weeks. Much later (in the last 6 months) some really specific exercises targeting the multifidus muscles , and reading "The back pain bible"  was eye-opening - having a good idea of what's going on in the back helped, and there were some exercises in there which with hindsight did help. I read somewhere (can't find it now) that once you lose the tone in your multifidus muscles, you don't spontaneously regain the tone/strength in them; other muscles cover for them and then you're in trouble.
At the end of last year I was at my wits' end - pain all day every day, no-one understanding what was going on, and being told by the chief physio of my NHS trust that "this is just how life is now" - despite me being the kind of obsessive person who actually does the exercises I've been set. So I decided to try things for a month and see what helped - some things did, some didn't (including a very expensive piece of mobilisation equipment). And the multifidus exercises (with leg weights) seemed to just 'switch on' the rest of me, allowing me to maintain good posture and protect my spine. I'm definitely not fixed yet, but I'm not in pain all the time - in fact I had a nearly 3 week period without a twinge last month, which was like being on holiday away from the usual hell. I really think the weakness in those muscles is the key to me actually improving for the first time in a decade (they were pitifully weak initially, and I'm sure there will be other areas where that's true). Maybe something that specific could help you?
For context, I'm 6'1 and around 90Kg with a fairly muscly build - I -look- fit and I'm certainly not overweight, but there's more to bad backs than appearances.
Anyway, hope that helps someone.
 - http://www.alexandertechnique.com/
 - https://www.amazon.co.uk/Multifidus-Back-Pain-Solution-Exerc...
 - https://www.amazon.co.uk/Sarah-Keys-Back-Sufferers-Bible/dp/...