Mirena

Sooo ladies I've been on the Mirena IUD about 6 months now so far it's been a good alternative for me. Helped with my heavy periods and cramping it's really helped with both. Until this month I've now been bleeding for over 2 weeks.. help!!! Is this normal or should I be worried?? I did read somewhere that this could be a sign it came out or got moved. Has this happened to anyone??