Melatonin (over-the-counter) works for a maximum of only three months.

I have an antihistamine prescribed called Zyxal (5 mg when needed)that helps with sleep very much.

You're better off to try 5htp Tryptophan for sleep than Tryptophan. (Tryptophan can't
cross the blood-brain barrier, but 5htpTryptophan can.)