Mirena Side Effects

I had the mirena inserted in Feb 2nd, and at first I had some pretty bad cramping, but felt fine about 3 days later. Starting 7th, I've been having waves of pretty bad cramps, some back pain, and some really bad gas pains. I also started spotting today, but I've never spotted before and it seems like a lot of blood. I'm so paranoid that I'm one of the like 1-5% with perforation or expulsion. Any other people have experience with Mirena? How long after insertion did you have cramping and/or spotting? Anyone else get bad gas pains?