1. For any given topic, please understand that you don't have to write about anything if you'd rather not. If your biggest mistake (taking this week's topic for an example) was shooting JFK, and blaming it on Lee Harvey Oswald, but you'd rather not incriminate yourself, no one will know if you just write about cheating on a final exam in high school instead.
2. There is nothing in the rules about writing non-fiction. In Season Two, there were two entries which were clearly fictional. There's also nothing in the rules about writing prose. Your entry could be poetry. There was at least one entry in Season Two which was a poem. As long as you stick to the topic, you're okay.
3. I believe there was a precedent set
I'm sure there are "true confession" type communities on LiveJournal, but that's not what LJ Idol is about. We want you to have fun, not worry that other people will think less of you for what you've written.
EDIT TO ADD: If you do write a new entry, please e-mail me at my username* at livejournal.com. I do have all the comments on the entry posts e-mailed to me, but it's possible that I would miss one, and direct people to your original entry by mistake.
*that would be onyxblue1, which hopefully robots can't figure out.