You're depressed
Just like with appetite, the physical changes of depression can swing to either extreme. You may suddenly find that you’re tired and sleeping all day, or that you can’t get a wink’s shuteye at all. A particularly common form of sleep deprivation is to find yourself waking up in the middle of the night, night after night.
Read more at http://www.besthealthmag.ca/best-you/sleep/8-reasons-you-cant-sleep-at-night?slide=2#6cGkLbW6DLRTKOxv.99