This is really starting to annoy me?

this boy he is a real , and he always call me fat (which i think he even weights more than me,he prob weighs lik 155 while i weigh 135,and because hes really tall he looks skinny) then he just said i hate fat bitches,which he was glaring at me when he said that, and i cant say anything back because he will start saying horrible stuff about me,the cl dont care they just laugh, they think he is cool but he is a real ,and the teacher can only send him 2 do detention which that does nothing because they almost,ALWAYS let him off theyll go "well dont do this again" and then they just let him go, once and a while he will get csi (detention),but that doesnt work,he will just come back and act the same,over and over again,everyday! go 2 detention come back. Nothing good comes from out of his mouth he curse so much talks bad about people.What happens 2 him,nothing!he gets a detention or get a warning.What do i do???Oh ya i knewed him since 7th grade hes been doin the same crap!