Melatonin and sleep

It does not agree with me. Took 3mg about an hour before bed. Fell asleep with little effort, then awoke, wide-awake with heart palpitations, anxiety, and total lack of mental focus. Would return to sleep, only to wake again in less than an hour. All the while, in and out of wild, vivid, hallucinogenic-like dreams. This continued all night. Not very restful. This was time-release melatonin, 3mg. I am on no other medication. This drug is obviously not as "side-effect free" as it's said to be. I will not use it again.

Taking Melatonin for getting to sleep. 3 mg at bedtime, would fall asleep in 45 minutes, around midnight, would wake at 5:30 with severe headache.