I sleep 12-13 hours a day (so your 9-10 hours aren't as bad as mine) but I feel alert during the rest of the day, now I am researching possibility that this might be connected with antidepressant called setralin that I am taking for about 5 years, or generally it's because of depression and the disturbance of chemicals seratonin or noradrenalin in the brain.

I can sleep for 10-12 hours a night and wake up and still take a nap in the middle of the day. During hormone fluctuations I can sleep 20 hours. If this sounds like you then you need to get in to see a sleep doctor. There is a name for what I have --idiopathic hypersomnia. You just wake up with it one day, but if you take your meds (Provigil or Ritalin) you are awake. My doc says it is like a switch in your brain is flipped and your brain is always thinking it's time to go to bed, so you feel like you're always pulling an all-nighter. Something interesting is that they've been treating more and more college age women with sleep disorders that are similiar. Whatever it is you should probably find a good doctor and maybe go to a sleep lab.