excessive sleeping ?

On an average day i can sleep anywhere from 9-13 hours and sometimes more. This use to be a thing i did on the weekend as a kind of luxury. I mean hey i was a teenager! But now that i'm in college i do it everyday. At first i just put it down to stress but then i went home for a week and still did it and then again at my grandmother's house where i relax the most. I've always had headaches, when i wake up i feel to groggy and i can't really think, my lower back will hurt or be stiff, and sometimes i feel like i've just been under a stressful time sometimes when i wake because my muscles are very tense. My roommate says its because i nap but i just cannot make it through some days without a nap. There are days when i wake up and the only thing i can think about is getting back to my bed. It's really starting to cut into my study schedule and i've already missed one class three times and i never miss class.`I'm so worried that something may be up and i'm so sick of being tired all the time. (also i've lost 20 pounds and still workin on losing more i just don't know what it could be.....) Thank you to anyone who post. Any information helps!