I feel you love, sometimes I feel like it takes an eternity to fall asleep, if I even manage it. We share the same thing you and I, I like to call it "over thinking everything and I can't shut my brain off" syndrome.
One advise I got from someone during a particular rough patch for me, was to start associating your bed with sleeping, and sleeping only. To have that be the only thing you do in bed. No more relaxing with your computer or doing your homework on there. Another thing is too try and tire yourself out during the day. I actually found an article that said "when you stay still for fifteen minutes, your body starts too fall asleep and eventually you as well. "
Distractions are always good as well. Like for example listening to music so your brain has something to focus on rather than letting your mind go to places you'd rather not. Me personally, I usually think of stories. Right now it's more of a fan fiction though with me and the Winchesters hunting some monsters down, you know normal happy things;)
I definitely suggest you check out the group "Night owls" here at blah too, you're far from the only one who has a hard time to wire down. It's full with great suggestions too.