sleep deprived? over sleeping?

i have been waking up tired and wanting more sleep for the past few weeks. most nights i blame my little doggie for crying by my bed wanting to sleep with me and not wanting to jump in the bed, instead she wants me to "carry" her into the bed, as a result she cries until her needs are met. if i count the hours of my sleep, i sleep at least eight hours. when i was still in school, i was good even if i have at least four to five hours of sleep. i would go to clinicals with that amount of sleep, attend a class and still have enough strength to hang out with my friends. but now that all i do is work 9:30-4:30 at the lawfirm and study until at 8:00 to 11:30.

is this fatigue feeling due to sleep deprivation? it can't be sleep deprivation for i sleep at least eight hours a night. is it sleeping too much, since my body was so use to being sleep deprived?? i would never find out the real answer to this, would i?