I know that you use the internet for more than 10 hours a day. I also know that you skip your lunch everyday just to return home early to use the internet. Plus, I am aware that your grades have been falling and you have been reprimanded by most of the teachers. I urge you to seek help from the school counselor.
I know that you do not want to admit to your parents about this and that they will not bother to understand your situation. I can help you. You can knock on the doors of the counselors room and tell him about your state. I am sure he will be delighted to help you.
Alternatively, you can tell your classmates about this and spend more time with them. I assure you that it will help to pry you away from the computer.