Joanne, I am not clear if this is a lump that has been there before and gone away and come back, or if it has been there constantly for 3 years.  Either way it is time to stop ignoring it and have it checked out by a doctor.  Since you are writing to a breast cancer site, you already know the worst it could be--breast cancer.  However, you may not know that it could be a non-cancerous lump or a harmless fluid-filled cyst.  Sometimes fear can keep us from taking action, or maybe you live far away from medical services.  Now is the time to find a way to see a doctor.  You may be greatly relieved to find out that this lump is not dangerous.  If it is cancer, a 2 cm lump is still at a size where your life could be saved.