Dear service user, Thank you for writing to healthcaremagic. I understood your concern. What happened to you, during first sexual encounter with your girlfriend happens very commonly to most of the individuals who starts engaging in sexual relationship with a partner. The problem is inside the mind, not in the sex organs. Let me explain. For constant erection, continuous exciting/romantic/erotic feelings should be there in your mind. If your mind is diverted to concern about erection, you will lose erection. You should only enjoy and only enjoy, without bothering about your performance or quality of erection or pressure to satisfy girlfriend during sexual intercourse. Relax and practice regularly above behavior method. No need to take any medicine at this stage. You may get counseling with your psychiatrist, sexologist or physician for this. Wish you good health. All the best.