take a hpt and see where that goes it's rare but people have gotten pregnant with the iud in if that is negative and you continue to have such pain go see your doctor just to make sure everything is ok like the placement. Do you check for your strings each month like you are suppose to?
I too had the mirena for almost 2 years before I had it removed, and every once in a while I would just "feel" pregnant...I never was though. My friend who also had the mirena thought she was pregnant a couple of times too..When I asked my dr. why I felt that way and he said that sometimes the mirena, well side effect of, can make you feel pregnant. Not saying that you are not, like the above poster said..Have you checked to see if the strings are still there? If you feel that you are I would wait a week or two and then take a pregnancy test..Im sorry I know I wasnt much help..
Even the Mirena IUD is not 100% effective it IS possible to get pregnant with an implant. Take an hpt or go see your doc for a blood test.