I had a similar problem. I ended up making this list so at least I had a routine to follow. Numbers 1,3,5 are core specific. I can do them all at home ( you will needs some weights and some other stuff but not a full gym )
I expect that I will get a bit of a flaming from the experts, but at least I am doing something which is approx 98.8 % of the battle. My back pain has reduced drastically ( but new bed has also helped with this ).
If I am doing it properly I work through the list sequentially, If I am being a bit slack or on the road in hotels etc I just do Number 1. You may need to google some the terms ( I probably made some up as well ) A pull up bar is needed for some of them but you can substitute, if you have not got one.
Number 1
Lying leg Kicks
Lying Leg Raise
Lying Ass Raise
Weighted rotation
Plank
Hollow hold
Number 4
Pull Ups
Kettle Bell Swing
Deadlift
Dumbbell Curls
Plank
Burpees
Number 2
Reverse Rows
Ab Wheel
Triceps pull down
Weighted squat
Weight Plate Lift
Mountain Climber
Number 5
Hanging leg raise
Leg swing rotation
Plank
Dumbbell chop
Ab wheel
Hollow hold
Number 3
Alternative arm/Leg
Lunges
Kettle bell plank
Kettle bell swing
Crunches
Hollow hold
Number 6
Kettle Bell push ups
Overhead Bar
Fly’s
Pull Ups
Triceps pull down
Weighted squat
Edit : List did not come out in order due to pasting, but you can work out the order I am sure.