What could pain in the side of chest just under the arm be, i have gerd and anxiety from withdrawal....?

Chest pain?: Chest pain should be taken seriously. If this is a symptom you have consistently suffered with your reflux, it may not be an emergency. Anxiety secondary to withdrawal from any potentially addictive substance can prompt chest discomfort - often in concert with other withdrawal symptoms like: sweating, elevated heart rate, nausea, palpitations, shortness of breath, craving, and headaches. See doc.