talk to an adult, but i know how hard it is to get an adult to believe you. dont isolate yourself, keep to the group that doesnt bully you, and talk to your parents about it. if they are good parents, they might take action.
i know how you feel, i had a teacher who took my stuff and showed all my drawings to the other students. maybe get online help? im not sure because i am struggling with the same sittuations.