Hilary, I don’t know if this will make you feel any better, but I got 5 cents per book (each one cost $16.95) for my first book, which was published by St. Martin’s. Most books sold by publishers don’t make back their advances. (Of course, the small publishers don’t even pay advances.) Keep writing. You’ll be wiser when you publish your next book. (Also, I do hope you have an out-of-print clause in your contract that will allow you to get your rights back. You can always re-sell your book when it goes out of print.)