Masturbation is normal physiological act and won’t cause any harm. Your method is not harmful. Your problem of early discharge is known as Premature Ejaculation. Premature Ejaculation is the most common sexual problem experienced by man. There are certain techniques, which can help you to stay longer. Kegel exercise is one of the very popular and effective techniques to control premature ejaculation. These are the exercises of pubococcygeus muscles (PC) muscles. A man can do these exercises anytime and anywhere and no one will even know about it. To identify the muscles of your pelvic floor stop your flow of urine next time you go to urinal. Contract the muscles tightly holding for 10 seconds i.e. stop urinating in between. Do this thrice a day repeating 10 times. The PC muscles control the urine and semen and firmness of your organ during erection, so keeping them strong will increase ejaculatory control. Even while masturbating you can practice stop and start i.e. rub for few thrust then stop for a minute and start rubbing again. Just relax on this, it should go away with some time.