No motivation, desire, or drive..

Normally I really enjoy school, I like to get my assignments done early and I study ahead of time for exams to ensure I'm prepared, but recently I've completely lacked the motivation, desire and drive to do anything. I have an exam and a paper due tomorrow for my favourite class, I haven't studied at all and all I've done for my paper is do research and find sources. I have no desire to get this paper done, nor do I have the desire to study for my exam, both of which have to be done for tomorrow morning. I don't feel up to do anything anymore. Today I could barely get myself out of bed.. the only reason I did is my dog was driving me mental barking and whimpering because he wanted me to let him out. Even still, I came back up to bed after I let him out. Again, he wanted out so I had to get up, after that I watched tv on the couch for a bit, then came back up to bed to work on my homework; which clearly isn't getting done. I don't know if it's depression coming back, or if it's just because I'm sick and severely lethargic.. Maybe a combination. I was happy when my plans for tonight got cancelled, my birthday plans, because I don't feel like leaving my bed. I just want to live here and not ever get up.