Hi,
According to your history it is your Quadratus Lumborum which are getting activated too frequently due to poor posture while sitting. Usually this happens when you sit more on one side of the chair unintentionally causing more stress to your lower back.
Next Steps
You can follow my instagram page (prehab121) to get free low back activation exercises
Health Tips
Try changing your chair, avoid sitting on the ground and just stretch minimally.