10mg is quite a high dose, the average dose for melatonin is 3mg, but I would discuss this with your pdoc and/or pcp on dosing if you choose to use this supplement.

There are many factors that could be causing your lack of sleep. You should try relaxing techniques such as meditating, yoga, reading, and some teas help reduce stress along with induce sleep like chamomile tea. I would address this issue to your pdoc or pcp today if possible as sleep deprivation is serious, especially for that length of time.