I had sharp pains in my left shoulder and under rib cage and 4 times to my heart. went 2 the er, they said i'm getting a cold. im 17,i don't get that.

See your PCP: This is an issue to be dealt with by a physician who has the time and facilities to evaluate this thoroughly. An ER is the wrong place for a reasoned assessment of a complex issue. See your family doctor. Would agree that this does not sound like a common cold.

Consider pleuritis: Considering your age, It is probably not your heart if you are otherwise healthy and robust. Pleuritis is ususally a viral infection that will go away with time. If you are having difficulty breathing other than from pain you should be re-checked. Please consider the accuracy of my answer from the perspective that I am an Orthopedic surgeon and this is out of my usual field of expertise.