Skyla pregnancy?

I have the skyla IUD and I have had it for two years this May. I am currently 11 days late for my period. I took a pregnancy at day 7 and it was negative. I on day 9 my boobs started hurting. I have never been late on the skyla and I am trying to decide if it has taken my period away or if I could be pregnant. Advice would be appreciated. Thank you!