I don't know if anyone has mentioned caffeine yet. Take note if that's in your daily routine. Oh too late, somebody already mentioned it.
You might also just accept that you need that kind of sleep and do everything you can to make it happen. If that means you don't take a 2 hour break in the evening, and study and do your assigned work in order to get to bed on time.
If you are certain there is no other reason for needing this much sleep, either physical or mental/emotional, then it seems a good start would be to ensure you get the required amount of sleep your body needs right now. This might not always be the case, but it seems for right now it's true. Relax, rest, and take care.
Just my 2cents.