In my 20's and 30's I suffered a lot of back problems. Now in my late 50's they are mostly a distant memory.
What changed is my understanding of the postural causes of the problem.
The worst period was when the children were very young, and I would sit for long periods bottle feeding on a sofa, then just enjoying having a sleeping baby on me. However my back was in a 'deckchair' posture. Coupled to that was the stance of lifting or lowering an infant into a deep cot.
My car at the time had a well worn and poorly designed seat, so my lower back was always in the wrong posture
Once the worst has passed, think hard about your posture, and try to get decent lumber support in every chair you sit in.
A good physiotherapist can be a lifesaver.