Hello, Thank you for using HCM. Usually the pain on the left hemithorax that spreads on the neck and the left arm originate from the heart. Nausea, shortness of breath while walking short distances, and the letargic state, support this idea too. l don t want to stress you but is better to see the cardiologist as soon as possible. In way to rule out the origin of the pain you need to have an ECG ( electrocardogram) and eventually a stress test. You should have some laboratory exams too. Once you have reached to a sure diagnosis, being treated is not so difficult and you may feel safe to continue your daily activities as usually. Meanwhile try not to get stressed, and do not much physical effort. Hope this may be helpfull for you. If you need further explanations, please feel free to contact me. Thank you, Dr. Juarda