Melatonin trial and error

I'm trying to find the correct dosage for me.

I was taking one 3mg melatonin pill an hour before sleep for 3 days and i would wake up to recall dreams, the dream recall would be longer than the last day....then all of a sudden i took a melatonin one night to wake up and recalled no dreams at all....and i felt kind of tired and groggy that morning and didn't even want to get out of bed.

Last night I didn't take ANY melatonin but i did drink a little bit of alcohol, and i woke up to recall a pretty decent dream.

Do you think that was because of the melatonin in my system from 2 days ago?

Should I try cutting a 3mg pill in half and take 1.5mg before sleep now? I think i'll try that.