I have excruciating pain in my lower abdomen when on my cycle, during a bowel movement only.... Please advise.

See below. Cells in the uterus produce a chemical called prostaglandin which stimulates smooth muscles in both the uterus and in some women it also stimulates the smooth muscle of the bowel. Muscle spasm can cause pain. To help with pain -omega 3 fatty acid & magnesium supplementation can be beneficial. Avoid excess sugar & low quality carbohydrates. Don’t add extra salt to food & avoid processed foods.