If you do identify some negative patterns, stop taking melatonin for several weeks to see if the problems disappear. If they do, seriously consider whether you want to resume taking melatonin. If the problem persists or is serious in nature, consult with a physician to obtain professional assistance. Any substance that has beneficial effects also has adverse ones. In this case, we are dealing with a human hormone.
Human hormones are extremely powerful substances.
We don't know what the effects of long term supplementation or single large doses of melatonin are. It may prove to be everything its proponents claim it to be. However, until we know that for sure, use extreme caution. Understand that you are being used as a human guinea pig by the nutritional supplements industry and paying them for the privilege.