Birthday Blues by Anne Cassidy
Published by Scholastic

Julie has been dumped by her boyfriend because he is now seeing Julie’s so called best friend Sara. Forced to find a new friend, she starts being friends with Tina – someone she’d never really talked to, but discovers is really nice. But Tina’s got serious problems of her own and because Julie’s still so wrapped up in her own problems it takes a while before she realizes that Tina really needs her help. This is a story of teenage friendships and pregnancy.