It’s like a hormone, so it’s not a question of empirical effects. It just works.

> I've experimented

I dont want to devalue your experience. But this experimentation is usually not "(placebo) controlled" and not "double blind".

You could! Take a randomly selected real-or-placebo, that's marked as such but you do not know at the time. See if you can feel the difference, not your experience, repeat. Then look at your results. According to placebo science the results may shock you.

I guess there's an exception to every rule! Do you ever feel sleepy at all? I would wonder why someone would use melatonin if they didn't want to sleep, which suggests someone who isn't sleeping well, yet it had no effect. Extensive suggests it wasn't just one dodgy batch of melatonin either.

I hope you're sleeping well now regardless. Lack of good sleep is like slow torture.