shingles can present as severe pain without any rash. But this pain can be due to other causes and the most important to be ruled out at your age is angina pain which can typically radiate to the left arm and armpit
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.