[Nightblood.]

I went through college/university (depends on where you live) without caffeine and undiagnosed narcolepsy so I know the feeling. Honestly, a strict bedtime routine is one of the best things you can do. If naps help, try to make some time for short ones when you need to be awake. It's possible you may have to take longer than the average person to finish. Consider lowering the number of classes you take at once. You can also probably talk to your teachers/professors and let them know you have a medical condition that makes you tired. You can also look into whether your school has a student disability office you could register with, it's possible you could get accommodations on deadlines and absences/lateness.