Boy is really upsetting me :( ....?

This boy in my school is horrible to everyone, he will be nice too you and then turn on you and recently hes started saying i have a moustache when i dont! and hes posting all over my facebook and screaming it at me in corridors. I dont even want to go to school hes getting me down so much, im seriously not sure what to do about him. Tell him too his face he will ignore me.