Well... Ive read somewhere there is people which functions better at day, and people which functions better at night. Im a night people. Unless i sleep 10+ hours, i always feel like shit in the morning/afternoon. But when the sun goes down i feel MUCH better, even if a slept few hours. Maybe its just how your body works.
Anyway, ive read a lot about this melatonin too. I dont think is a good thing to force your body to work in a way different of its "normal" way (in your case, being a night people), but if you really must do it, i think melatonin is worth the try.