[PaulHoule]

This book is the best one on the subject

https://www.amazon.com/Treat-Your-Back-Robin-McKenzie/dp/095...

The core idea is that most back pain is caused by the shortening of the muscles in your back. "Posture" is not a productive way to think about it because you don't have the flexibility to be in the correct posture. If you try to improve your posture without addressing flexibility you will feel more pain.

The exercises in that book will help, also try the "Cobra" position from yoga, and also this exercise

http://reichandlowentherapy.org/Content/Practices/Grounding/...

If you stand up and do the "bow" whenever you have back pain you will probably feel better pretty quickly (1 to 2 weeks)

If you are popping NSAIDs or tylenol, also consider the antidepressant Venlafaxine. It is often highly effective on chronic pain, particularly things like back pain that definitely have a stress-related component.