Cramps...

So, I figured out that after I stopped taking my birth control pills my periods are really painful and heavy, worse since having my daughter, but i've noticed a week or so after my periods I get this really severe cramping in my lower abdomen like where my uterus is and then the cramping goes to my butt and I'm not sure what's going on. It's not like a dull pain.. it's a really sharp kind of pain. I just had my daughter about 6 months ago and have never experienced any kind of pain like this in my life. This never happened before I had my daughter. I was just wondering if any women out there experience this too? Or should i see a doctor about it? All i know is that it hurts really bad and I don't know why.