I'm On The Mirena Iud, Have Been For 2 Years

I'm on the mirena iud, have been for 2 years now. I haven't had my period for almost 3 years (since I became pregnant with my son, who is 2.) The past few weeks I have been feeling very fatigued even with plenty of sleep and Im extremely bloated. The first thing that I thought it might be is pregnancy, but I took 2 home pregnancy tests (one today and one last week) and got negative results. What else could it be?