Period pain is common and a normal part of your menstrual cycle. Most women get it at some point in their lives. It's usually felt as painful muscle cramps in the tummy, which can spread to the back and thighs. The pain sometimes comes in intense spasms, while at other times it may be dull but more constant.
Why is my period really painful.......
The cause is usually having too many prostaglandins, which are chemicals that your uterus makes. These chemicals make the muscles of your uterus tighten and relax, and this causes the cramps. The pain can start a day or two before your period. It normally lasts for a few days, though in some women it can last longer