Suffered from those back problems for years. The ones, where - for no reason at all, you suddenly feel it go.......and know that you are in for several days \(at least of severe pain). Used to put mine down to my gymnastic coaching, which involved lifting, etc the gymnasts.
No good reason what caused it 'to go'. Once, just as leaned down to pick up a crisp packed on the floor, another time when I sneezed, a third, particularly bad one, when I was sitting outside painting the shed. (That time, I could not move and waited until my teenage son came out into the garden to as about tea, and he helped me into the house and onto the sofa.)
The only thing (in addition to painkillers) that I found helped on those times were an electric heated pad. Few years ago, I did actually have a spinal fracture after a fall, undiagnosed for several weeks), and that pad was an absolute life-saver.