Been taking 6 mg melatonin every night.  Last night I forgot to take it for the first time in ages.  I noticed today my head felt lighter throughout the day, felt "clearer", possibly less depressed (again "lighter", less "slowed down") (don't know if I am imagining this but pretty sure I'm not), also felt like I was breathing better (have bad allergies so don't know maybe that was a coincidence and allergies were just not as bad today).  I would like to stop taking it, but don't know if this is wise, is this what is keeping the headaches away is the melatonin use and am I imagining that maybe it is causing "side effects" (although relatively mild)?  Any advice from long term users or others knowledgeable?
Thanks--any input appreciated.

Yeah, you know you're right I'm not going to take the risk--there's a reason why I've been in remission this long and I have a feeling that that word begins with "M" and ends with "N"!  Otherwise why would I be shadowing right now?  Yep, I'm not messing with the sleep thing, I don't want those headaches back.

Maybe you could try taking only 3 mg of melatonin before bed?  I too have experienced the "heaviness" of my head taking 6-9 mg of melatonin.  I did some research on line and discovered that excess melatonin production has been linked with SAD, Seasonal Affective Disorder.  Resulting in tiredness, grogginess and difficulty getting out of bed.  So I now only take melatonin when I am afraid a cycle is approaching and then when the cycle is over I lower my dosage, gradually until I am not taking any.   Reading the leaflet with the melatonin that I purchased, the recommended dosage is 3 mg and it is not recommended to take it on a continual basis.  I realize that everyone is different, but this works for me.
Hope you are still in remission...

Next day groggyness is one commonly mentioned side effect of melatonin. For daily maintenance, I usually take 1.5 mg; when I am getting hit, the dose increases.