Wendy,
I take 3 mg of melatonin but it is '6-8 hour time release' and even if I wake during the night have no problem going back to sleep. I usually take it about 1/2 hr. before bedtime. Works well and sleep was a problem for me as well. I feel rested in the morning and usually get 8 hr. of sleep a night.
Also use a light in the winter.
Sunflower