If your on the mirena and your periods stop your most likely not pregnant.. It happens with mirena... But the mirena also causes infertility, i had mirena, it was placed Feb 2012, it was removed Oct 2015... It has been 2 yrs and i havent had a period.. Not once.. I cant have another because of it.. If you EVER want to have a baby or have another one this is NOT the birthcontrol you want to use..