Hello Thanks for query. You have not mentioned whether you are engaged in sexual activities with female partner or not before knowing how to increase sex stamina. You had been indulged in masturbation since many years and now worried about your sexual potency in future . First of all I would state that there is myth in a mind of common man that excessive masturbation is the reason of all sexual problems But I would like to state that it has been discussed in scientific forums all over the world and proved scientifically that masturbation does not have any negative effect on any organ or system in the body.All the problems that you are facing now are mind related and due to anxiety. Following measure will help you to boost up your confidence and getting good erection and help you to have enjoyable sexual life in future. 1) Practice regular exercise for 45 minutes followed by meditation for 1/2 an hour in the morning. 2) Take high protein diet rich in vegetables and fruits and Vitamin A,C,D,E.and Zinc 3)Take anti oxidants like Almonds 5-6 everyday.. 4) Avoid alcohol and smoking.. Dr.Patil.