Why do i still cramp after my period ?

Prostaglandins: Something that happens during your period is the release of prostaglandins that cause your uterus to cramp and expel the old lining of your uterus. Those prostaglandins can sometimes still remain after all the blood's gone and cause cramping. Old blood can also be irritating and cause cramping as well. This is normal as long as it doesn't go for much longer after the period.