Naproxen gives me great relief, but I'm worried about the side effects. What should I do?

My doc M, prescribed Naproxen 500mg co for my spine, hip, knee pain. Then M, sent for many rx. He also suspects problems with my left meniscus (MRI to come). I broke tibia-peroneal in 3 places, near the ankle, in March 2014 with result of 2 rods and 12 screws; all of this is removed in June 2015. Then, since then, still have pain back, hips, even if physio and / or chiro always. Then, this Naproxen relieves in 1 tablet half of my pains! Wow! What worries me is that he forgot to tell me how long I should take the Naproxen (prescribed 12 x). Will I become ACCREDITED? Consequences? My doc is retiring in 1 year... thanks for your great site: finally something sensible,