What Causes Period Like Cramps During Bowel Movements?

Hello, since I was pregnant (my son is now 1 & 1/2) before and during my period I have period like cramps but really bad and when i need to poo. I am guessing the pain is actually to do with my bowel/intestines and sometimes i actually feel faint when i need to go. I am also really bloated around the time of my period. Otherwise I am healthy with reasonable diet and active lifestyle and do not suffer from diarrhoea or constipation. Thank you