It's an online book called Gaby, and it's about a boy named Drew, and situations keep coming up where he has to dress up as a girl. it originally starts when his mom makes him dress up as Gaby, Xena's sidekick for some charity thing, and then whenever he's in drag, he gets called Gaby, and there are 120 chapters now, with some side stories, and it's good so far, and I'm pretty much addicted to it.

http://www.sapphireplace.com/stories/bell.html

The site where it's hosted at