hi.. thanks for writing.. i have understood your concerns.. erectile dysfunction is usually because of psychological issues at your age. reasons may be: anxiety and stress going on in your life, anxiety about sexual performance, depression, sex in a hurry, lack of stimulation while masturbation or sex. sex is more than just penetration, there is a role of foreplay in holding the erection for long time. you shud get proper stimulation from your partner. foreplay shud be continued even during penetration. if you have any stress or anxiety then it will divert your mind during sexual activity and thats why you can not concentrate on sex and lose erection. proper visual and tactile stimulation is necessary. in my opinion, you shud consult a psychiatrist or sexologist and undergo sex therapy. in which you will be given knowledge about sexual organs, sensitive parts and foreplay etc.. do not take any drugs without prescription from yuor psychiatrist. i hope this will be helpful to you,, best of luck..