I have the opposite problem. I wake up by 5 am every day even when I don't have to be up. In fact I almost never have to get up that early. Doesn't matter what time I go to bed either - 9, 10, 11, 12, 1. Up at 5, sometimes earlier. Never set an alarm. Leaves me tired though in the middle of the day.
Of course the only exceptions to this are when I really really have to be up super early to cram in some studying - on those days I tend to wake up late! Wish that could be everyday, sleep is so nice.