Hello, Here are few causes I have mentioned: 1. Masturbation in one session for a long period of time may also result in pelvic congestion which may lead to pain. 2. Pain may also be related to how you are positioning yourself during masturbation. If your testicles are moving around too much, this motion could be the reason behind your discomfort. Consider a change in position or try cupping your testicles with your free hand as you are masturbating. This touch could also benefit by providing extra sensation and may make the experience more enjoyable. 3. Epididymitis can also be a source of testicular pain following ejaculation. This is caused by inflammation in the epididymis (the tube behind each testicle that stores and delivers sperm). The most common cause of epididymitis is a bacterial infection that can be the result of a sexually transmitted infection (STI) or coliforms (bacteria that live in the intestines). The infection can usually be cleared up by a dose of antibiotics. Complete examination of genitals may require please consult your physician he will examine and treat you accordingly. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Penchila Prasad Kandikattu