What should i do? when my friends are making fun of me?

i have 2 friends. they are each others best friends. they have been best friends since the 2nd grade. i met both of them in the 6th grade. now were in 8th grade. they are mean to me. they make fun of me and embar me in front of my crush. right now they are currently mad at me because i cant go somewhere with them and i was there ride there. they write on the desks and call me ugly, lie to me all the time, make fun of me because im bi and like one of our friends, and more. i have to stay friends with them cuz if i dont they will tell my mom that im bi and went out with our friend and i have a myspace. and im not allowed to have a myspace. and my mom doesnt know im bi. and im afraid to tell her i am. they are like 2ce my size. both of them, so i cant really punch them. i would wanna be like that anyways. im not like the type to get in fights. i dont know how to fight. i dont know what to do. im so sad. and i dont wanna tell my guidance counslor or my mom cuz then they will say something and then i will be known as a tattle tale. help me fix this! pleeeeeeeeeease:(