I need to sleep, but I'm not tired, please help?

I asked this question before, but I left out details that aren't getting me the answers I want. So I've tried tea, music, television, but nothing helps. And I don't have medicine I can take to help. I need to get up early, and I just can't sleep. I'm modeling in a fashion show in two days and I can't afford to be looking sleepy- plus it runs late. I also have two exams tomorrow not to mention I need to be learning stuff in school, so I need to be awake. Please help?