heycal, it sounds like your thoracic region might not have a very good posture, and it definitely will affect the lower back along with the leg usage and pelvis balance. As you go through the exercises and therapies it would be very useful to learn a bit about the concept of posture in general. If you are motivated try the following book. It's one of the best imo.
The New Rules of Posture: How to Sit, Stand, and Move in the Modern World
Well trained, strong breathing muscles are central in thoracic posture. Check out this book.
Breathe Strong, Perform Better