HELP!

Emma
So recently it's been super hard for me to sleep.. and I've come to notice that the only time I can really fall asleep and get a good nights rest (like at least 6 straight hours) is if I fall asleep in my BF's arms. I can be sooo tired, but as soon as I crawl into bed alone.. nothing! 
We don't live together and can't spend every night at each others houses.. HELP! Why can't I fall asleep anymore?!