Interestingly, I have found that excess mass can also feed into this. I was carrying too much muscle for my core/back/hamstrings to be able to handle at about 17 causing issues with my lower back. These reoccurred in my 20s due to an increase in fat %. The only thing that ever guaranteed they went away was losing mass, be it fat or muscle. Now a few years on I'm able to carry a little bit more due to flexibility work and strengthening my core. Also, worth bearing in mind that the hamstrings all the way up to the middle back should be looked at as a one when trying to correct back pain, don't neglect those hamstrings!