Wrong format?

I just got a new MacBook Air, I'm a complete newb to the system, so I hope that someone can help me out.

I copy/pasted a huge document from a Pages trial to the TextEdit program and saved. Everything looked fine then. I shut the document yesterday and opened it today and it's all jumbled in code instead of properly formatted. Is there anyway to revert this to the original format I saw last night? Please, I'm near tears. This document is my novel, and I'll have to rewrite the ending if I can't reverse this.