I have been hurting in my left arm pit for about 2 months. It isn't swollen, no lumps in breast or under arm, but what was just soreness now keeps me up at night. I can't lay on the left side because it causes too much pain,. It has stared in the last two weeks to shoot pain in/around my back left shoulder blade, and when I lay on left side for very long it feels like something is squeezing my breath away. My husband threw his arm over me one night and it hurt so bad I sat up. If I lay on my back, I can still feel the pain but not as bad, right side eases most of the pain, but my right arm goes to sleep. I breast fed my children, have had a hysterectomy, and am otherwise very healthy.