Hello sorry to intrude into your thread.
In regards to your usage, when you wake up did you immediately open your curtains and let in light, usually the taking of extra melatonin is aligned with Light Therapy to get the greatest use from said product. If when awake you still lie in bed for a further 1/2 hour then your not training your body to perform its "duty" properly.
Also when did you take it ? You have to take it at the very LEAST 2 hours before bedtime, Melatonin is put into the blood earlier than the brain's own production and acts as a mild hypnotic so taking it 10 minutes or indeed anything under an hour and a half before bed negates any usefull effect.
The dose in your case doesn't cause sleepiness but timed correctly some hours before bedtime, can add about 30 minutes to the advance of your bodys produces its own melatonin starting about two hours before bedtime, provided the lighting is dim.
This is known as dim-light melatonin onset, which helps keep the body on a regular sleep-wake schedule. It also helps prepare the body for sleep. Which is why keeping the same wakeup - go to bed time is pretty vital if you wish to achieve any sort of ability to achieve total restfull sleep. If your chopping and changing sleep patterns (ie Sat night go to bed at 5am) your body is constantly adjusting so it can never quite guess what the hell time you wish to begin production.
Also do you have dark Curtains ? If not get them and cover your lighter curtains, even a dark sheet will do.
Second get rid of all light sources in your room, i put my 2 alarm clocks under my bed so the light from it is not visible. Even better is get rid of ALL electrical producing items from your bedroom.
If anything i would reccomend, 200-600 (dose dependant) of Magnesium. Citrate seems to work best take 1-2 hrs before bed. Excess magnesium in the blood is freely filtered at the kidneys so its next to impossible to overdose, though at high levels it will cause bowel movements. So dont go TOO high.