Birth control Insertion

Okay so this morning I went to see my doctor and got my first ever IUD inserted and OH MY GOD the pain that I felt during the insertion process and I know they say you will have Cramps and Back pain but does anyone know how long I will have to deal with the cramps and back pain?

I chose the Mirena IUD instead of the copper because I get really horrible heavy periods. And the Mirena says it will lighten your periods and cramps or sometimes you may not get a period. Does anyone have experience using the Mirena?