What's your schedule like? The only time I felt like you was when I was working a job during the week. All of my days were basically 8-6, I was tired all the time and I lived for the weekends.
But, my anecdote aside, my advice would be to try and study smarter. If you have time in between classes, try to get work done then. And maximize your class time, take good notes so you can be lazy later. Unless you're overloading on high level classes, I think there should be enough free time to keep you sane.