You are at an age when your hormones become very active. Some drugs have been touted as anaphrodisiacs but there is little evidence they work at all to lower your sex drive. Many males in military basic training suspect there is something in the food because their sex drive becomes virtually non existent. It isn't something in the food, it's the increased level of exercise and being kept busy constantly for the entire day.
Whether what you're experiencing is excessive would have to be evaluated by a doctor but I suspect you aren't getting enough exercise and have too much time to think about sex. Get busy and get active.
That happened to me as a kid... Except not always thinking about sex. Like Rob said, Get busy and/or active. It will help you get your mind off of this... habit.
If you are going to post an answer to a question please ensure that the answer/comment is related to the comment, this makes no sense at all in regards to the current question.
Engage yourself into some sort of physical activity if possible. For me, I take football and try and get my thoughts deep into football. How to run a play, trying to memorize them. How i'll take someone down when we get pads. Make a commitment to yourself to stop. If you do masturbate another time, do something like 20 push ups. Or clean your room. Basically sorta punish yourself whenever you do it. Hopefully this helped.
idk if you're overweight or not, but overweight guys have more estrogen which makes them last longer during sex/masturbation, and makes errections occur more often