It usually begins at about ages 12-13 and continues until a woman is about 50 years old. Menstruation, or the menstrual period, is the monthly bleeding that occurs as a part of a woman's reproductive cycle. Most women have mild cramps as the menstrual period begins-having such cramps for a day or two each month is usually normal.
Some women have severe pain.
Painful menstruation is called dysmenorrhea. I have pain during my periods. Over half of women who menstruate have some menstrual pain for one or two days each month. If you are a teenager, this is very common. The pain usually eases off in a few years, though women in their twenties or older can also have pain during menstruation.