Terrible bullied at school for years an this year is gonna be the worse? What can I do?

I am gonna be 18 an still a freshmen cause I have failed my school 4 times (1 time in 8th grade an 3 times my freshmen year). All of the bullies I had before (Shawn, Brian, aspecially Mark Kerner) has all graduated now.

But now their is this guy who is a freshmen name Charles an he is like 6 feet tall an 250 pounds an he is all muscley an stuff. He use to call me names at the bus stop when I was in 6 grade an he was 2 grade an it really upset me an when I would ball he would laugh.

I learned that when people bullied me to just ignore them, if they was saying mean things or even if they hit me (or like when Shawn shot me with a watergun full of pee) to just ignore it an look straight a head an even if the tears come rollin in not to scream or ball, just sit their an look straight a head an not let them know your scared cause if they know they will bully you worst!

But Charles wont stop, he has punched me in the stomach so jard I had to go to the e.r. an he farts in my face an stuff an even if I ignore him he just waits.

What can I do? I cant change schools, I am already on probation cause I need 25 credits to graduate an I only have 3an I have to be promote this year or I will be expelled an dad said if I am expelled I have to sign up for the service an go to Korea an Russia for WWIII!

Somebody help me please! I cant report Charles cause he is a foot ball star an when he punched me that time an I went to the e.r. I got detention an he got nothing!