Lots of potential things going on here. To my totally non-specialist eyes I'd guess you're not reaching some state of deep sleep that you really need, even though you sleep a lot.
What is the light quality where you sleep? Even small rays of light disturb some people's sleep.
What is the noise like? Ditto.
Have any roomates or other people told you that you snore?
Have you noticed or your dentist noticed that you clench or grind your teeth?
What is the temperature like in your room? Generally I've read that people sleep better when the room is colder and they have blankets than warmer with less blankets.
It sounds like your doc shrugged you off. The "I don't wake up feeling rested" directly contradicts what she replied to you. Go back. Insist on standing up for yourself. This is interfering with your life in a big way. Tell your doc exactly what you told us. Print out your forum post. Make your doc read it as you sit there with them.
Too much sleep can also be a manifestation of depression - I'm not saying you are, it just might be something to consider.