What Causes Spotting,nausea And Sore Breasts While On Mirena Coil?

Hello, I've had mirena for about 8 months now. I had a few periods in the begining but nothing since december three weeks ago, I noticed my breasts feeling sore, so I thought I was going to start my period. I had almost no spotting. Just a tiny bit of pink on the toilet paper once a day for about 3 days. Nmy breasts are increasingly sore, I have been very tired, light headed and naseous after I eat asnything.. I am getting a blood test tomorrow woud this be a waste of my time?