I recommend yoga.
If you could do this movement very morning when you wake up and evening before going to bed, you will alleviate all pressure in the back:

With your straight legs and straight back just bend down your head towards the floor. Don’t force it; just let your head approach slowly the floor, only by the gravity effects... try to be in the position at least 5 minutes always aiming to reach the floor with your head.
It won’t happen immediately, maybe it will never happen, but the process will stretch your back and will certainly alleviate.

Again, try to practice yoga. It will have a positive impact as most of back pains are caused by lack of stretching.