Sleeping disorders. Do I have one? I'm always sleepy.?

For some reason, I go to sleep for a normal 7-8 hours, I wake up tired and throughout the day I am stll weary. I know I don't sleep too much because I've had shorter nights. I have the same routine: wake up at 6 and go to bed by 9 or 10. I eat regularly so I have energy also. Would a doctor be able to tell me what's wrong?