I need help sticking up for myself?

theres a boy at school that has been giving me **** for a few months now, his spreading rumours about me and trying to get his girlfriend to bash me. im over fighting with him and i want to say something mature but not too bitchy that will make him stupid, he never says anything to my face only over text or facebook and he is a wimp in person, i need help please help. By the way we are 14 and he used to be my bestfriend, and he gave me more **** until he found out my boyfriend would hurt him if he says anything else, please help