I keep getting bullied. What can I do?

I am only in 8th grade and I get bullied everyday by the same people. I will not mention there names. They have done lots of things to hurt me both physically and mentally. They are in just about every class I am in so they can bother me whenever they want to.
Here are some things they do to me. They got everyone in all my classes to call me the "Nerdling" some stupid nick name because I am bad in sports and I wear glasses, They threaten to beat me up after school if I dont give them my lunch money, They keep telling people not to let me play and join in, They make fun of my passions and hobbies like playing Chess, reading books. They call me everyday to tell me Im ugly.They hurt my feelings so much I cry alone in the toilet. They put this letter in my locker saying nobody likes me. During recess they shove me and steal my glasses, I cant see anything without them. They say stuff like, Oh, You smell like fart and every time I talk they make these gagging sounds. They say stuff like "Your so different from the rest" or "Your so useless at everything" and that makes me feel really bad. They say all these nasty things behind my back. I feel really ashamed of who I am with everyone calling me a "Math addict" or "Book worm" and "Nerd". I did not tell a teacher because they might think I cant do things on my own and think less of me. I dont want to tell my parents because I dont want them to worry about me. I cry almost every night praying things will get better but they dont, It only gets worse. What do I do? Please give me advice.