Thanks for writing to HCM. I understand your concern about masturbation and penis size. Masturbation is akin to sexual intercourse. What penis does in vagina during sexual intercourse, same it does during masturbation in your folded palm! This is a natural activity. Not a disease. Just as sexual intercourse cannot lead to weakness or erection problems, so how masturbation can do it? Masturbation should not be at the cost of sexual relationships with your partner. This needs open sharing of likes and dislikes of either partner. You can go for pathologist to have semen analysis. Important and more practical fact is that the size of penis has nothing to do with sexual satisfaction of the partner. It is entry followed by continuous thrusting movement considered as sufficient. The method of lovemaking according to partner s preference rather than size is more important. Sexual sensations are in the outer aspect of vagina i.e. the clitoris, inner lips and lower one third vagina. Inner two third of vagina is largely insensitive. Wish you good health.