Slight discomfort in my left arm and shoulder and slight shortness of breath on occasion, should I be worried?

I'm 21 year old female and have noticed over the last few days a very slight discomfort in my left arm, shoulder blade, and left side of my chest. I was also noticing at work a slight shortness of breath to the point of me hyperventilating, but only when I am focusing on it. I have a perfectly normal resting heart rate.

Now, I work in a coffee shop and because the temp inside is 70 and outside it is in the low 30s it is quite stuffy inside. I noticed this after working on the espresso bar for about five hours straight during a very unusually busy day (nonstop mochas). My left arm is the one I pump syrups with. Could it be that I might've just overworked the muscle? I am pretty out of shape.

Someone made a joke the other day that I might be about to have a heart attack, and of course that made me freak out. The shortness of breath and discomfort seem to only get really bad when I am focusing on it and/or become worried about it. Is it in my head?

First of all consult a doctor because it is the doctor who will be able to advise better. Secondly take a break in between when you work. Come out and get some fresh air. Move your hands a bit. I hope this works.

Check out these related products from Amazon: