Alice has given really good advice, I would definitely focus on getting back in rhythm with your showering etc and, what worked for me was forcing myself to sit down at my desk for 30 minutes and just choosing some work that I had to do or some revision. Building up gradually.
You should try and find out why you're feeling depressed, is it because your grades aren't good? If so, laying in bed isn't going to help things.
I would also speak to someone about how you're feeling because it'd make you feel better, especially if you see a counsellor, this situation is very common for them.