I was wondering how bad this habit of mine is?

UHH YEAH. see your doctor or school therapist to find options to make you feel better and find your motivation and to start you on a better sleeping cycle. Talk to someone about this, it's best to let someone know. Cold meds aren't good to take if you don't have a cold, taking too much can even cause liver damage, and THAT is scary. So please, find help in someone you trust.