Hello and welcome to health care magic.
The most important thing to rule out for a chest pain
with breathlessness and radiation
of pain to left arm is an acute myocardial infaction or heart attack
There are different types like stable angina
and unstable variants depending on the type and nature of pain and factors associated.
My advice is to visit your physician and get an ECG /EKG and cardiac enzyme like Troponin T . If it's normal then there is nothing to worry about.
Other causes that can produce similar features are costochondritis
or a left sided pleural effussion. Your doctor will search for the other causes once MI is ruled out and will treat accordingly.