The most common causes of pain at the vaginal opening during sex are as follows: 1. The most common cause is vaginitis, because patients with vaginitis will have vaginal congestion and edema, and will have increased vaginal secretions, which may cause pain when the area is stimulated; 2. 3. It is caused by the damage of the vaginal opening due to too intense sexual life; 4. It is also seen in patients with urethritis, because local congestion and edema occur in urethritis, and when you have sex, the stimulation of the vagina will stimulate the urethra, so pain will occur. The actual pain can be caused by the fact that the urethritis is a result of local congestion, edema, and vaginal irritation.