the best way to know is to go to ur ongyn and let them do a pg test
Because of the mirena you can show false positives but you also have .1 percent chance of getting pregnant. But the mirena is made to make your body feel pregnant so it is natural for your body to show signs of pregnancy. You should get checked just in case so the baby is not hurt by extra hormones but it is doubtful that your pregnant mirena is a very very effective birth control