Is prone masturbation dangerous? i've been doing it all my life. does it cause permanent nerve damage or infertility? how do i stop?

Not harmful: What you have been doing will not harm your health. If you wish to stop, stop, no medication is needed nor one exists for your symptoms. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex.

Sensitivity changes: Frequent male prone masturbation places pressure on penis & nerves at its base & may cause numbing to arousal / pleasure with other positions. Seek help for delayed orgasms, erectile dysfunction or inability to achieve orgasm in other ways. It may lead to back pain in males & females. No to fertility changes. REF: https://www.healthline.com/health/healthy-sex/prone-masturbation#effect-on-sensatio