Hi Thank you for asking HCM I have gone through your query.It is usual to ejaculate fast when masterbate.Size of penis does not interfere with sexual performance because only 2 and half inches of vagina is sensitive.If you are getting early ejaculation in normal sexual activity you can try following methods.You can do squeeze and stop technique.You can deviate your thought to something nonsexual when about to near ejaculation.You can stimulate your partner to maximum before getting yourself stimulated.You can put on a condom or condom with anesthetic which will decrease the excessive stimulation on penis and prevent premature ejaculation.If all these not helping then you can approach an Urologist or sex therapist or psychiatrist for behavioral therapy and medicinal management like anti depressants.Hope this may help you. Let me know if you have any further query.