I Am 45 Yar Old Female. Not Every Month, But

i am 45 yar old female. Not every month, but evry 3 to 4 months, I get such bad pains the couple days befor my period and first day. I cant stand up straight, lot of pressure and bloating. Hurts to go number 2, feels like a knife inside. A pee more than usual too. What could be up?