I've had chronic insomnia since about the age of 13 and melatonin literally saved my life - long periods of little or no sleep can do really awful things to your brain. These days I take 1mg tablet about an hour before bed, takes me about 30 minutes to get to sleep after lights out, and I wake up feeling perfectly fine.

My wife though can take the same dose, same routine, and report similar symptoms to you. I wonder if her body technically doesn't need the additional melatonin but mine does.