Primary dysmenorrhea is caused by increased prostaglandins in the uterus leading to painful contractions without an underlying condition, while secondary dysmenorrhea results from conditions like endometriosis, PCOS, or pelvic inflammatory disease that cause pelvic pain with menstruation. Common symptoms include lower abdominal or pelvic pain, diarrhea, nausea, headache, and loss of appetite. Diagnosis involves a medical history and physical exam, and may include ultrasounds or laparoscopy. Treatment focuses on pain relief using analgesics, prostaglandin inhibitors, muscle relaxants, a soft diet, hydration, and heat therapy.