What Causes Pelvic Pain And Cramping Before Having Periods?

Hi my name is Lela I m 22, my conserns are about knee dropping pelvic pain before my period. I m 4 days away from my period an today during sex i started feeling pelvic pains around my ovaries an then after sex the pain got intensive. It went away about 20 minutes later but I encounter this every month an then during my period the cramps are even worse. What could this be?