Mirena IUD - 6 months in

Lindsey

I have a couple questions about the mirena IUD and wanted to ask you girls before I called the doctor to see if you all have experienced any of this. 

I had my IUD put in about 6 months ago, and for the first 3 months I experienced heavy cramping constantly and pain during sex. I went in to get it checked along with a pregnancy test because I was having symptoms of being pregnant (extra tired, moody,etc.) everything came back just fine and my test came back negative. I've loved the mirena because it has changed my extremely heavy and painful periods to light sporting over the course of 48 hrs.
My most current period has been very different though, I was back to my regular periods, as if I didn't even have the mirena in. Has anyone experienced their mirena falling out? Or is this common after 6 months have having the IUD in?