That one is obvious: question too broad ... does not compute ... out of cheese error.
Back pain is a massive, massive thing - it sometimes doesn't actually involve the back. Here's an anecdote:
I (50ish y/o male) used to have episodes of quite crippling to very crippling "back pain". To cut a long story short, I found at least two causes (can't remember the medical term - indicator?) and sorted them. One was putting my wallet in my back pocket - sounds innocuous but it puts pressure on the buttock involved and skews your posture slightly. The other was seemingly ridiculous: When turning over in bed, I used to flick myself over by performing a sort of torsion twist about my spine. That's fine when you are 10 but not 30, 40, 50 etc.
Nowadays I simply avoid silly lifting postures and all is generally good. It took about four or five years to recover from past habits.