Severe cramping pain

I have the IUD almost 3 years now, I frequently get really bad severe pain to where it maybe when I'm supposed to be on it. But I'm not. I don't get it. And have never had a period while using IUD. But this pain is so severe I am considering taking it out does anyone else get this? And not have a period? I've been to the doctor and they say there's nothing wrong and it's in place etc. Im dying :(