What Are The Side Effects Of Mirena IUD?

I have had the mirena for 2 years and over the last 2-3 weeks, I have had consistent movement in the mid to left side of my abdomen. It feels like fetal movement. Not fluttering, but movement. I have taken 2 home preg tests and both have been negative. I have seen a few places online that false negatives can occur in the second trimester. It's driving me crazy. I feel it moslty when I'm sitting but also when I am walking.