Could I be ?

Breanna
So Ive been on the Skyla IUD since 02/2016 &my period has been normal..well i haven't had a period since May 4th &I've already took 2 test that has came up negative but now when I press on my stomach it's hard in certain places &feels weird...idk what to do from here. Could Skyla be causing false negatives ? Any advice is welcome !