Hi , Welcome to HealthcareMagic Forum.
Your friends are right, it is indeed called Masturbation
. You have attained puberty
and masturbating since a younger age is not at all harmful. It means your Hormones are working right. Not to worry as it wont have any adverse effect your future sexual life and do it only when you are sexually aroused may be around twice to thrice a week. Practice Yoga
and eat healthy nutritious balanced diet. Exercise regularly. This will improve over all General appearance.