I cannot believe you haven't been talking to your teachers if you are failing their class. They are the ones that can give you options. Have you asked for help, gotten a tutor, asked someone in class for help, talked to the teacher????? Your teacher should be the first one you go to if you are having trouble.
Most of the time, students are never held back if they fail a class. It just means summer school, or if you're in high school, retaking the class so that you have enough credits to graduate.
So, talk to your teachers and see what they recommend or go to the office and find out what your options are. Don't put this off - bad news doesn't get any better no matter how long you wait.