You may have way too much on your mind. It happens to me when I cant stop thinking about something of someone. I am sure that you cant sleep because you are thinking of that certain someone. Hang in there, I know that you are strong.
Get your mind off of the situation...Focus...Breath deeply.. Rest...Consentrate...Love will come...Let the past go...Love will come...Think on good things...Love will come...
Maybe you're under stress and have a lot of things on your mind. I don't know anything about your life so I can't quite decide. If it gets serious, you might want to see a doctor.