why do i need him?

my boyfriend and i have been together for a little over a year. im not a clingy girlfriend, and nor do i feel the need to talk to him everyday and watch his every move. but i've recently noticed something strange. since i have sleeping issues, im never able to fall asleep at all. and whenever my boyfriend stays over i fall asleep at night with ease. and when he leaves, im up for hours unable to go to sleep what so ever. it's not that he's boring, and it's not that im up thinking about what he could be doing...but could this be because of the sex? or could how well he comforts me? any thoughts?