your MRI reports suggest their is disc buldging at l4- l5 level which could be one of the reason for your low back pain . Also you mentioned of injury at your back which could be the reason of your buldging disc and muscle stiffness.
Next Steps
I would advice you to continue with the physiotherapy sessions still you dont get rid of your pain.use hot packs thrice a day for 15 mints, do some back strengthening and stretching under strict guidance of physiotherapist. also continue with yog therapy as it is helping you with your pain.
Health Tips
Avoid prolonged sitting and standing posturesas it can aggrevate your pain. Keep on changing your positions to release the pressure and avoid lifting heavy weights