OP, I do think you need to calm down, and take the time to understand the Yakkan Shoumei rules and understand what we are saying.

I looked up the Japnaese customs form. On the back, the relevant question for you is "Do you currently having her possessions narcotics, marijuana, opium, stimulants, or other drugs, swords, explosives or other such items?"

1).As long as you're not taking opioids or cannabis to sleep, you should be able to safely check off NO to that question. (Yes it does say "other drugs," but Tylenol and Zantac are technically drugs also, and I really doubt travelers carrying those are checking off NO to that question.)

2).If whatever sleep med you take is on the list of psychotropics on that above link I pasted and you're bringing in less than the specified limit amount, then you should be fine.

Just relax and enjoy the trip. Otherwise I'm afraid you might end up doing/saying something weird at customs.