For months now I've had a feeling that something is under my left breast. I can't feel anything externally, I just feel like there's something there. It's like a foreign body sensation and sometimes it feels like a pulling sensation. It is not painful. I notice it more in certain positions such as when I'm lying down in bed or sat slouched on the sofa. I also sometimes feel it when I'm stood up or move my hands above my head. Sometimes it feels like it's under my breast, other times it feels like it's actually in my breast and other times the sensation moves across my abdomen to a more central location. Any ideas what this could be?