Are you going to sleep later than normal recently?
Sounds like your body clock may be out of sync.
happens to me sometimes, gets to the point where i can't get to sleep till 3 or 4 am
Best thing to do would be to set an alarm for 6 am. Get up straight away. complete your day as normal, but don't take any naps during the day. by around midnight you should be feeling pretty tired and should hopefully drift off to sleep
Getting up early really shocks your body