<s>[INST] When I lay on my left side there is sharp pain under my ribs and pain shoots into my left arm then it goes numb. Only relief when I cease the position. No pain or discomfort at any other time. Pain for two days. 47FemaleCaucasian5'5"140 lbsNo history of high blood pressureNo history of heart troubleBoth cholesterols normal [/INST] Dear,I undestand your concern.You need to do a cardiac electrocardiography (ECG) to exclude cardiac causes. If in the ECG track, there is no sign of cardiac problems the next step is to check your breasts. If there is any nodes or a change in colour.This two steps would help you track the right cause. If none of them show results, then there is a chance for Herpex virus which also comes with this symptoms, when it achieves to Zoster Herpes Virus phase. This is common in people with low immune system.I hope this clarification somehow will orientate you.All the best,Dr. Eni </s>