I fell asleep at 11 pm and took melatonin at 10 pm. i woke up at 2 am and tried to fall back asleep. it is 4 am now, and i usually get up around 6:30.

Short half life: Melatonin has a very short half life. Even the Rx version - Rozerem (ramelteon) is only prescribed for sleep onset. However resetting your sleep architecture takes time and patience. Here's an article from the Harvard Medical School which might help - good luck! http://www.helpguide.org/harvard/how-your-body-clock-affects-your-sleep.htm