Mirena and pregnancy

Hey, so i got the mirena at the very end of November. So i have had it 9 months. I havent got my period since the beginning of july and it has been coming regularly every month. I have been having a few pregnancy symptoms like: nausea, smells making me nauseous, dizziness, headaches, and cramping when lifting something heavy. But every test i have taken has come up negative. Ive taken one a week for 3 weeks. Has anyone been in my shoes and not been pregnant? Can the mirena just stop your periods after so long? Any advice or experiences would be appreciated!