I have been doing cardio and working out since around November and have lost about 32lbs so far. My fitness is increasing and I can see some great results, but lately my chest seems to have some muscle type pains in it when I breath deeply. These sometimes feel like they are between the shoulder blades too. I'm pretty darn sure they are not heart attack symptoms because it is not a tightness in the chest, but kind of a deep ache at times. Has anyone had similar growing pains while increasing fitness and losing weight? I was thinking this could be related to the diaphragm but not sure. Sometimes these pains can be more prevalent at night while I'm sleeping or trying to sleep.