My friend won't stop bullying me Help me plz!?

I have a friend that keeps bullying me and that person keeps calling me "Gay" , and a nerd, etc.. (even though im not like gay and stuff) I ask why to him why he calls me that stuff and he says that you study alot for my school's spelling bee -__-. ) And i gave him examples of Other ppl who studied and it still didn't work... Furthermore, well i think have alot of good grades and get good test scores or something.. (not to brag) How can i stop this bullying :(