Hello thanks for asking from HCM I can understand your concern and first of all I would like to tell you that size of penis doesnt have much role in potency or intercourse. The size of about 5 inches is perfectly normal provided if you are getting proper erections. The size is measured from dorsal part of penis or from base near testis to tip. Coming to your second problem. Premature ejaculation is common in some individuals. There is no need to worry about your future married life as it can be treated easily with some non-medicinal methods and medicines. Diverting attention away from intercourse during sex is one very useful technique to prolong erection. Kegel s exercise, Start-stop technique are very useful. Consult a sex therapist for details. Medicines like Dapoxetine are also effective. The medicine is prescribed on SOS basis and need prescription from a psychiatrist. Herbal medicines like Tantax Royal also have excellent results. Consult any good psychiatrist for treatment and counselling. Thanks, hope this helps you.