Painful BMs during period?

Since about a year before I got pregnant with DS I started having this issue during my periods.  
During AF my lower abdomen is tender and my butt gets super painful. It hurts to even sit on it. And having a BM is hell. I get sharp pains in my lower abdomen and I get some serious pain in my butt. I always just thought it was slight constipation or something but I always seem to go, it just hurts like crazy. Sometimes it hurts so bad I start shaking and crying.  
It only happens during my period which is what's weird to me. Is this normal?