Sleeep

Is it me or does everybody get more tired when they get more hours of sleep? I think that is really weird because if I get 7 hours of sleep I feel great throughout the day.  I feel happy, energized and ready to take on whatever I need for that day.  But if I get a little more, lets say 10 hours, I feel beyond tired throughout the day.  I am more sluggish and unwilling to do anything.  I have always wonder why is that? I always thought the more sleep you get, the better especially being a teenager.  I heard from countless of people that a teenager should average 9-10 hours a night, but is that even true?  If I get 9-10 and I feel more tired than I was the day before.  It feels like I did not rest at all.  I really do not know why it turns out to be that way, pretty weird if you ask me.