Over the years i have treated hundreds of people with back pain. As a Chiropractor I am not immune to back pain myself, after all we are all human.
So when it comes to posture, the one thing that I find helps me more than anything else, is to make sure I remind myself to stand level.
Think of you legs as two pillars of a building, if one of the pillars takes on all the weight, this affects the whole building.
This is not as simple as you may think, and you have to constantly remind yourself to stand upright. In my experirnce it is worth it though, and over time as your muscles get used to your posture they will work to support your new you.