I have the same problem. Although I experienced it before I had my Mirena.It has been out about 3 months. I have fibrocystic breasts.Do you have that as well? My breasts always get really sore right when I ovulate. I experience the feeling that you describe every once in a while. I know exactly what your mean. I got my hormones levels checked and the results came back normal. I thought I could attribute everything to low progesterone. I don't know now.