I have had pains in my upper body right between my breasts just below them for a while now. hard swelling there as well. i am also having difficulty to breathe and am nauseous. what causes that?.

ER can evaluate: Shortness of breath is not normal, unless it is the mild temporary shortness of breath with sports activities (but even then, one must be sure she is not having more shortness of breath than her sports peers have). Possible reasons for chest and epigastric symptoms include heart attack, pneumothorax, pericarditis, acid reflux, pneumonia, costochondritis, etc... ER can evaluate for heart attack.