Suggest doctor & treatment to cure my sleeping problem.

I have sleeping Problem as I am not getting fall asleep early in bed,it will take 1 to 2 hours to fall asleep,and mind always thinking, if there is a happiness it is difficult to sleep, or if I am sad also difficult to sleep, this problem is since last 4 - 5 years, 
Please help me to get out of this problem. Please suggest me any sleeping medicine which is not dangerous to be taken.