Spread Extremely Thin

I need to learn how to be mean and say no. It's day 2 of my 6 weeks of hell and I'm mentally and physically wiped. I wake up everyday at 8am, go to class from 9:30-10:45, go to class from 11 to 12:45, go to the rec for an hour, an hour break for lunch/random stuff, go to class from 2:45-4:20, sprint to my car and make it to work by 5, then get home around midnight, do homework for all 3 classes, get up in the morning and do it again. I've only done it for 2 days and I figured out that it isnt' healthy. Especially since between noon Monday and noon today I have lost 4 pounds. That what eating a total of 2 sandwiches and 2 cups of yogurt in 2 days will do to a person. I hardly have time to pee, let alone eat. When my boss asks me tomorrow to come in on Thursday I'm saying no, I only wanted to work 20-30 hours a week and I'm at 25 and its Wednesday. I should totally be sleeping instead of typing this. That's what I'm going to do.