Hello Rohit, Welcome to healthcare magic forum. Your problems of penis shrinkage and premature ejaculation are most likely due to excessive masturbation. Masturbation is a healthy adult sexual behavior. Like other behaviors, when over practiced or addicted it can lead to both psychological and physiological imbalances. The side effects of such changes to the body include: * Fatigue. Feeling tired all the time * Lower back pain * Soft / Weak Erection of penis * premature ejaculation i.e early release of semen fluid * Groin / Testicular pain * presdisposition to urinary infections Also it may hamper your future sexual life psychologically and physically. So for now try to focus your attention on other aspects of life like hobbies, family, career and decrease your sexual urges .Such abstinence may help your body to regain the normal hormonal balance and genital function. If you have problem in abstinence, then at least decrease the frequency or use masturbation only when absolutely necessary.If the problem of weak erection and premature ejaculation persists even after a couple of months of such abstinence then you may consult a sexologist for further evaluation and management. As of now dont worry, its very common problem in young boys and it usually resolves soon. Wishing you a healthy future. Regards