Hey, there!
You CAN use Lulu.com for your project and keep it private - there is a function that allows you to be the only one who can access the file and print copies for your own use. It won't show up on the catalogue and thus no one can get a copy other than either yourself or who you allow access to your account.
*However*, I would be thinking about what you want to do with this book first. If you want to send it out to publishers, do *not* send them a bound and printed copy. They'll want to see the unbound, paper version. As well, depending on how much circulation your book has had they may consider it to be "published" and pass on it - it all depends on what you want for the future of the story.
DO NOT fall prey to some scam outfit like PublishAmerica who will offer to "publish you for free" and then try to sell you back your own copies.
If you want to pursue a legitimate publishing contract for the book then keep it safe, keep it close and don't print it out. Save it to a DVD and then start polishing it for sale.
Good luck and see you at NaNoWriMo!