So 3 days ago I had TERRIBLE back pain, like couldn't stand up and it was in my thigh and butt area also. I was supposed to start my period yesterday, and I didn't. I'm always early, and never irregular. I have the mirena, and I am sexually active with my husband. Should I be worried? I took a test and it was negative, if I did end up pregnant we would be ecstatic, but worried since I do have the IUD!