Is it normal to spend days on your own doing nothing?

I feel like i have lost the will to do anything. I have lectures and essays to write so i go in to uni to do them but when i am back home i spend the day in my room alone in the dark not wanting to do anything. I cant even muster up the will to eat and have about a small bowl of rice a day just because i have to. the only other time i leave the room is to have a cigarette. I don't know what is wrong with me i mean nothing traumatic has happened. i do get like this every now and then but it has never been for such a long period of time. any suggestions?