This girl is so annoying! help me please :(?

theres this girl in my 5th period that always makes fun of me! i try making fun of her back, but kids say shes the toughest girl in the 7th grade (yes im in 7th grade), and even though im a guy, im terribly weak, and im scared of getting hurt by her. and my friend says she hates me cause of a head problem i have, it keeps moving but i try to stop my head from moving. ive been trying to stop for 10 YEARS! so its basicly a problem i have. i try to tell her, but she just keeps ignoring me and making fun of me, EVEN WHEN I DONT SAY ANYTHING! she said that i...."do" the terminator every night. i was disgusted! and she asked what i asked for breakfeast, and she made it into dirty little jokes and all the others girls just laughed. UGH! i wish she was gone! i would try to ask the teacher, parent, or counseler for help, but she would just get mad at me and hurt me. what should i do? :(