First of all, your brain needs sleep. It's pointless to study for that long because you won't retain anything, so yes, you will be wasting your time. Like someone else said, study for 2 or 3 hours at a time and take a break for about half an hour (eat, watch tv, anything. As long as it's not remotely related to school).
Secondly, have you tried youtube for help. I swear, I would have failed a few classes if it wasn't for youtube. Go to youtube and type in khan academy. He explains everything very clearly. Good luck.