my self 29 years old . i am masturbating from last 10 years. my problem is i am not able to hold erection for long time may be 4-5 minutes only. as soon i release my semen it looses its erection please help me. before may be 3 years i use to get lots of semen but know quantity of semen is also reduced to very little . help me please , i get frustated if not able to make it for long and my marriage life is also getting disturbed.