Worm story - Morris Gleitzman

Wilton has no tendrils, no friends and no idea why he's so different to all the other microbes in his stretch of the intestine. But now he's had enough. He's going where no microbe has gone before. To the end of the known world, where the sludge gods dwell. To discover if he truly is a microbe. Or maybe a worm? Or possibly just a noodle that can talk?
After an epic journey, Wilton and his new friend Algy find their way back home, and discover that the true key to saving each other, their world and their 'janet' lies not with the sludge gods, but with themselves.