Mirena IUD with sudden bleeding and cramps!

Avery
hey guys. I'm 17 and I got my IUD inserted about two weeks ago. the procedure was minimum on pain. and I was so happy for that. afterwards, I had zero cramping but quite a bit of spotting (not as much blood as my periods though) and the spotting stopped three days ago. 
My period is in eight days and yesterday I had the worse cramps I've ever had. far worse than the pain for the actual insertion of the IUD. I was bleed a lot and and I used three super sized tampons yesterday. and now, today, I have no cramps or blood. what the heck was it? 
I'm just wondering if that little weird period day is normal and if anyone else experienced it? I'm an only child and I live with my dad so I don't really have any girls around to talk about this lol. I really appreciate it!