(Mature Question) Do NSAID pain relievers really reduce...?

First of all, it is a good thing you stopped taking Naproxen on a daily basis because it is very, very bad for your stomach lining. I'm hoping it wasn't a doctor who recommended you doing that. Every so often is fine. As far as the heavy bleeding, wait until the next period comes and see how it is. I doubt if the Naproxen lightened your flow. If it heavy next month, go have a check up with you gyno to make sure all is well. No two periods are alike and they will change from time to time as you age.