Seek out the advice of a qualified physician always, but I can tell you: I get this too. My symptoms are:   Stabbing/throbbing pain on the left side of the chest, ribcage area near the breast and sometimes including pain in the breast. Temporary immobility (more from fear of aggravating the condition) Trouble taking deep breaths due to stabbing pain   I believe that a combination of little things can combine to bring on this pain; most of all, pressure that builds up due to things like trapped gas, forgetting to breath or not breathing correctly, and having larger breasts, which are more prone to painful pressure from ill-fitting bras the thin straps of which create a pressure point at the top of the shoulder and the bottom of the breast when not fully or adequately supported. Oddly enough, I sometimes get it when just lying in bed when I am not wearing a bra. In this case, I believe that gravity creates its own pressure. I heard that fuller figured woman should sleep in a bra but I just can't get comfortable like that. For anyone else who suffers from this, my suggestion is to be fitted for a very supportive bra, preferably one with wider and/or cushioned straps. These bras can be expensive, though. If you're worried about cost, then Just My Size and Cross Your Heart each make a bra constructed for full-figured women with wide straps and fuller coverage.