Whenever i take melatonin to help me sleep (about once every couple of months) i always wake up during the night feeling wide awake. why is this?

Melatonin-excess: Melatonin helps with sleep onset and is a good option if your sleep-wake cycle is misaligned with the usual sleep-wake hours, however it does not help one to remain asleep and can cause premature awakening in those who have appropriate timely melatonin production. Too much melatonin can cause anxiety, irritability,depression (all of which can cause early awakening) and rarely even hallucinations.