Normal body weight depends upon the height and body fat distribution. If your height is less, then thus body weight can be considered as normal. One must also consider the fat component in your weight. Masturbation habit is unrelated to body weight. If you are troubled with the habit of masturbation, you must consult with a sexologist.
Next Steps
Kindly consult with a sexologist for further management and detailed instructions. For more information regarding this matter you can consult me directly via practo.