Last year I got the Mirena put in and immediately started having issues. Along with the bleeding I had constant painful cramping and was bloated. It also felt like I was gaining weight, but it could have been the bloating. After about 6 weeks and after discussing it with my gyno, I had it removed. The pain immediately stopped.
I know I've heard the bleeding stops eventually, but can last for quite some time (I have a few friends who love it because they rarely ever have periods with it in) but my doc said for some, the bleeding continues or like with me, my body probably saw it as a foreign object and it was trying to expell it (thus the severe cramping).
Follow your gut (literally). My body knew something was up and it didn't want that thing in there. I know many have had success if only they can get through the initial bleeding. Good luck.
H. Hunter
http://www.AZActiveKids.com (my website for parents in Phx)