Having chest pain, mostly on left side, can feel pulse in neck and it's fast and hard to breath. heavy chest, very exhausting to breath.. what is it?

It is... time to...: See a doctor. Chest tightness, chest pain, and shortness of breath can be due to minor problems or to very serious ones. An E.R. doctor can check to see what might be going on. Sometimes, tests and chest xrays will be done. Possible causes include angina / heart attack, partial pneumothorax (collapsed lung), asthma, reflux, heart arrhythmias, etc... One should not wait around with such symptoms.