Hello Thanks for your query.Based on the facts that you have posted it appears that you have a deposition of smegma a secretion of the glans penis beneath the foreskin. .It does not need any medication.You have to clean it everyday while taking bath. You had been indulged in masturbation since last 12 years and now facing problems related to sexual activities.First of all 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 scienificaly 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 measures will help to boost up your level of confidence and allay anxiety and there by improve your sexual performance, 1) Practice moderate exercise for 45 minutes followed by meditation for 1/2 hour. 2) Take high protein diet rich in vitamins A,C,E,D.fruits and vegetables . 3) Avoid alcohol and smoking . 4)Take some anti oxidants like Almonds 5-6 everyday. As regards the lengthand girth of penis it is absolutely within normal limits. Do not worry and get married. Dr.Patil