My friend has been a huge jerk lately, what can i say to him so he will shutup?

Ok, so i have a good friend of mine that goes to my school. The problem is, it seems that most of the time he is trying to make me mad and he is trying to annoy me. He isnt much taller then me though he is stonger than me. Im a pretty skin person. He likes this girl and the girl likes him back, today when ide talk to him all he would talk about is his big muscles and hede keep flexing them, he was being a showoff. I said please stop cuz i didnt care about his muscles, then in P.E class he was annoying me. It seems that he can annoy me and im not aloud to do anything to him to annoy him back, though i cant annoy him or hell hit me back(sometimes it hurts allot). He's taking advantage of my size. Then i ask him why hes doing this and i get mad at him, and he tells me to man up and not stop being such a baby. Then i say well ur being mean to me, then he just laughs and sais i like to tease you. What hes doing isnt teasing me, its bullying me. I have to admit i have a high tempor sometimes. In science class he wouldnt stop flexing his muscles at me so i said, HEY, WHY DONT YOU GO FLEX YOUR MUSCLES IN FRONT OF YOUR GIRLFRIEND(no one really heard.) By the way i like this girl in gr.7, so hes like, why dont you go ask out that girl you like in gr.7? The girl your addicted to, then he kept saying it and everyone heard, that was mean of him. Though most of the time hes making me so mad. Then when i tell him to stop he thinks its a joke. I DONT want to go to the principal and tell on him. Though what can i say to him so he can shutup? Oh simetimes he makes fun of my high voice.