Have you always had this problem? Maybe you are just inherently a night owl.
One thing I would suggest is up your carb intake, especially at dinner, so that your body feels more comfortable when it's going to sleep. Another suggestion would be to making sure your room is pitch black.
Also, what time do you normally wake up? Is it consistently at the same time? Maybe you need to spend a month or two just waking up at 6am and going to bed at 10pm at the latest.