It is normal for your age.But too much is bad ,what ever may be. Best option is to avoid watching porn regularly. You can divert your mind to so many things in life like taking care of your studies ,your physical fitness etc. Once you learn to divert your mind from daily watching porn to something else,you will be enjoying your masturbation better and time will get prolonged as it happens once or twice in week. so dont masturbate like brushing your teeth. best of luck