Back pain after ejaculation may be caused by spasm of back muscles, herniated lumbar disc, fasciitis of lumbar back, kidney disease and so on. 1. Back muscle spasm: the symptoms of back pain after ejaculation are related to the back muscle spasm caused by frequent and excessive sex, and the muscles will continue to contract violently, which will lead to pain. 2. Lumbar disc herniation: weaker muscle strength will lead to disc herniation, disc herniation will lead to discogenic back pain, will also lead to muscle soreness, inflammatory substances oozing will lead to stiffness, leading to back pain. 3. Fasciitis of the lumbar back: Fasciitis of the lumbar back muscles can cause chronic aseptic inflammation, which can cause pain and also lead to back pain after ejaculation. 4. Kidney diseases: Many common kidney diseases, such as nephritis and kidney stones, may cause back pain. Sore back after ejaculation may also be seen in soft tissue inflammation, osteoporosis and other diseases, if the symptoms of sore back after ejaculation, persistent and unrelieved, you need to seek medical treatment.