Such pain is often caused by a musculoskeletal
disorderAdjustment disorder
Anorexia nervosa
Asperger syndrome
Autism
Autoimmune disorders
Bipolar disorder
Bipolar disorder
Bleeding disorders
Borderline personality disorder
Bulimia
Chronic motor tic disorder or
nerveNerve biopsy
Nerve conduction velocity compressionCompression of the median nerve
Cpr - adult
Cpr - child (1 to 8 years old)
Cpr - infant/inflammation. If accompanied by tenderness, it is almost always muscular. In that case you should make a careful inventory of the physical activities you engaged in, prior to the onset of the pain.
If it seems to wrap around your chest from back to front, it is likely to be a problem with one or more of the nerves between the ribs, called intercostal nerves. Other causes include gastroesophageal reflux, with "heart-burn". The pain could also be due to a viral pleurisy, sometimes called, "The Devil's Grip" or pleurisy due to clots to the lungs.
The EKG is a good sign but not a guarantee that the pain is not coming from your heart. However the continuous nature of it and the lack of an association with exercise would be atypical for coronary artery disease. You may have to have further testing.
Bottom line is that this is most likely a benign pain and will resolve spontaneously, over time.
...maybe this is why it is not always on the same side??? ...if discs in your neck (or other prob?) move... i am not medically trained, just been through a lot with musculoskeletal problems...
until God heels us, wishing you His best