I am anj 18 year old boy . i'm addicted towards ...

http://www.healthexpertadvice.org/advice/Addictions/Stop-Thinking-About-Sex-269.htm

Your options are to seek professional help or to realize the deleterious affects of your actions.  It appears to be turning into an unhealthy obsession and you must take control. You are the captain of your ship and if your behavior does not change there are no good consequences that will come from your obesessive behavior.  Occassional, self-gratification is actually normal but when it begins to consume your time and keep you from doing constructive things, that you know you MUST do (like school), then you are obsessed and you have a problem that needs to be resolved.  Get a handle on it (excuse the pun) or you will find yourself in MAJOR trouble because of it ... You're 18 and at the doorstep of manhood.  You have to be more responsible.

I don't know if you would call it an addiction or an obsession.You say if you relieve your sexual desire once a day you are good for the rest of the day. Why is this affecting your studies? If you are relieving yourself in the morning before going to school you shouldn't be having any problem during the rest of your day. First get rid of all your girlie magaizes and find something useful to do instead of concentrating on your obsession with sex. You may need some counseling to curb your appetite.Having a good sexual appetite is normal, but you seem to take it to far when that's all you think about. Get a life, like sports or anything that keeps mind and hands busy. Seek advice from your doctor and see what help he can give you. Good luck, and I hope this helps.

Sounds like all 18 yr old boys

Yup, sounds pretty much normal to me. Though it also sounds like you actually need to learn how to masturbate.

The reason why most individuals fail to stop masturbating is due to expectations. You likely have said to yourself, "How can I be cured from this?" or "How long will it take for me to stop masturbating?" Change your thought process! This kind of thought process actually feeds the addiction and makes it worse. It is a set up for continued failure. It is like telling yourself to stop breathing, eating, or sleeping. The intense masturbation cravings connect to the same survival parts of the brain that eating, drinking, and sleeping do.
You have trained your body and brain to use the behavior of masturbation as a survival process. It has become a part of life just like eating and drinking. Pornography in some form usually becomes a tool to feed the behavior. Will power alone is simply not enough.
You need to retrain your brain so that you gain control of your life.