TweetHow are you for sure, did you have an MRI?
Our backs kind of have a mind of there own, when they are stressed and/or strained they have a protective switch to put it in easy terms, that kicks in to protect it from any further injury. Most mild strains take anywhere from 4-6 weeks to heel, depending on the individual and 'WHAT THEY CONTINUE TO DO ONCE THEY ARE INJURED"~!
If this area has been injured, you usually feel it during respiration and lateral flexion, it may feel as though someone is stabbing you, kind of a sharp pain, or may be slightly dull, while inhaling or exhaling. The pain can also be caused from weak/tightness in the muscle, which will in turn cause pain as well.
Here's a good stretch for th Quadratus Lumborum~
https://www.viddler.com/explore/chrisgrayson/videos/86/
Stay Strong~~!!!
IPL