Asleep but not really asleep?

I really dont know how else to put it and its even harder to explain. ok let me start off by saying that i have insomnia that i take ambien for. Now when i say im asleep but im not really asleep i mean that i will try and go to bed, and i will like fall asleep but im not really like asleep where like i will be thinking about what i was thinking about before i went to sleep and i will not have any dreams, when i get out of this trance i will look at the clock and usually a few hours have passed and i can tell that like i never actually fell asleep but i was just like stuck there, also how i know that im not actually asleep is when i get out of it im not groggy at all its like im perfectly awake right away, anyways sorry for the bad detailing but its really hard to explain.