Hi Thank you for asking HCM I have gone through your query.Regarding the size of penis:Only 2 and half inches from vagina is sensitive.So the larger size is not needed to satisfy an woman.Masterbation doesnt decreases your power.But try not to do it excess which is not good. If you are getting early ejaculation (Premature ejaculation) during normal sexual activity you can try following.You can do squeeze and stop technique.You can stimulate your partner to maximum before getting yourself stimulated.You can deviate your thought to something nonsexual when you about to near ejaculation.You can put on a condom or condom with anesthetic which will decrease the excessive stimulation on penis and there by prevent premature ejaculation.If all these not helping you can approach a Psychiatrist for behavioral therapy and medicinal management like antidepressants.Hope this may help you. Let me know if you have any further query.