If 10+ years of treating back pain has taught me anything it's down to improving 3 things:
1 - Deep core strength
2 - Trunk & pelvis mobility
3 - Freedom of movement of legs in sockets
There is a playlist on YouTube that address all 3 of the above. Also if you master this you can progress onto the Improved Posture playlist, then Pilates Fit.
Here is the link however if you feel like you need to be kick started with some 1:1 tuition see Back Pain Healing Sessions.