What Really Happens When You Try To Go To Sleep

For some reason I can't ever get to sleep when I want.  Whenever I'm super tired in the time it takes me to put on my Pj's, brush my teeth, and actually get in bed, I've moved around enough that I'm awake again, so here's how my usual night goes...
I'm so tired I can't even stand it

So I go to bed but by the time I get to bed...

So I decide to check Facebook to pass some time

So then I surf the web on my phone

And there isn't so I attempt to sleep, but I can't get comfortable

And inevitably I hear a noise, and assume that there is a murderer in my room

Then FINALLY I fall asleep