But for anyone reading this comment, there are two things I want to share, from hard-won experience:
1) Back pain and posture are incredibly complex and counter-intuitive, and come from a complex interplay of biomechanics, perception, and emotion. Anyone who says "just sit up straighter" or "just strengthen your core" or "use a standing desk" or "stretch more" or "it's a muscle imbalance, go to the gym" or "do yoga" doesn't know anything. Even if you think one of these helped you, it depends on the individual and they can do even more harm than good depending on the person. I think there's even more popular quackery in posture and back pain than there is in nutrition, and that's saying a lot. Even most doctors don't have the slightest clue -- which should be self-evident, given how many people have back pain and how it's not getting fixed.
2) The best place to start is "The New Rules of Posture: How to Sit, Stand, and Move in the Modern World" by Mary Bond.  It's the only book I've come across that takes the right holistic approach, but still maintains respect for "hard" science, explains the theory (medically, not according to any "school") but also gives you guided exercises. Start there, and then once you've gained a decent understanding of your body, you'll be in a place where you can figure out what more specific techniques you need, if you do (e.g. whether Alexander technique or psychotherapy).
So I call Somatics "Advanced Feldenkrais".
Having back pain that won't go away isn't normal.
A lot of pain I’ve experienced over the years has been caused by an imbalance in flexibility between muscle pairs. Lately I’ve been having issue with the pectoral minor vs. one of the rotator muscles that’s been making overhead pressing a very pinchy experience. Releasing the pec minor with a lacrosse ball has done wonders for improving the comfort (and power) of my overhead press.
My only beef with this process is that figuring out which pair is imbalanced is really hard, and I could never do this on my own. It is not intuitive or logical that a pain I'm feeling in my shoulder can be fixed by focusing on my chest.
It's just I hear so often that the problem with someone's posture is a weak <insert whatever muscle here> contrasted with a normal <opposing muscle> and that the solution is just to go to the gym to strengthen that muscle so they'll be balanced, which will fix the posture... and that's virtually never the case.
For example, how many viruses all basically make flu-or-cold-like symptoms? Have you read about the array of symptoms that a person with MS might - or might not -experience?
Back pain is more like that first category, though. Lots and lots of things can cause it, so it really does depend on the individual. Hard science means we can do some investigations, know what is the more normal causes of such pains, and start treatment from there.