Does Stomach Bloating And Nausea After Mirena Insertion Indicate Pregnancy?

my doctor inserted an IUD - Mirena last May. My last period was on 11/9/14. My stomach has started to grow and i feel bloated and have been feeling nauseous and my breast are painful. I took a HPT and it was negative. I eat healthy and walk 2.5 miles every day. Could i be pregnant?