Pain in vagina opening before period is this normal?

No: Premenstrual and menstrual pain originates in the uterus due to prostaglandins, chemicals that are released in high concentration when the lining of the uterus breaks down. They cause significant uterine muscle contractions resulting in uterine ischemia (lack of oxygen to the uterine muscle) which results in cramps pain in the lower abdomen and lower mid back area. Vaginal pain would not be normal