Could be puberty, yeah. Voices generally change during that period of time so it would make sense. My advice would just be to strongly work on your fluencey *now*, before it gets potentially worse. Just like anything medical, attacking it early is the best bet. Not sure what your remedy was the fast few years, but if that doesn't work again, try all types of stuff. You might be surprised when one random strategy suddenly works really well. Best of luck! Let us know what goes on.