Why am I sleeping so much?

Ever since I've been on Christmas break from college, I've been sleeping a lot. I need to sleep for about 10-12 hours every night just to be able to get out of bed. Then I will get up and go eat something b/c I'm hypoglycemic. Anyway, after I eat, I'll watch TV for about an hour. Then I'll sleep again for about 2-4 more hours. It's annoying that I'm so tired. I try to stay up but can't. I'm just so tired. Does anyone have any ideas as to why I'm so tired? I went to my doctor, but he doesn't seem too concerned. I still am, though.