Everyone's first time is unique and different. This is a fundamental fact. However, it is critical to be prepared for sex. How can you do this? Firstly, you should be willing to have sex with your partner, and you must explicitly give your consent to the same.
Uterine muscles contract and frequently relax when women are on their periods to expel the inner lining of the uterus. This causes menstrual cramps during periods. Self sex results in relaxing the vaginal wall. This increases the blood flow to the pelvic region, reducing menstrual cramps.