Think of it like when you are moving around busy it's like they are in a car and that can make you fall asleep. lol that's how I think of it

So since I'm laying down they move because they wake up since I'm more calm then being active

That's because when you're active, the baby finds comfort in your movement and often times it puts them to sleep... and when they are awake you can't feel them because you're moving so much. While you're laying down, they're awake because the movement has stopped. Kind of like if you were rocking them to sleep.