You were a chubby girl and often got bullied for it. That caused you to stress eat which made you get bigger, which then caused you to get bullied even more. It was a loop that never ended. Sam, the most popular guy in school, noticed it and felt really bad about the bullying because he genuinely really likes you the way you are. He tries to befriend you and get close to you but all that went through your head was that it was a prank and his friends were just going to laugh at you.