What could be causing trembling in my chest and shoulders along with weakness and loss of appetite?

About 2 months ago I started getting odd unpleasant sensations across my chest and upper back, trembling and loss of appetite. When this happens I feel somewhat weak and need to lie down. I've had 6 different blood tests, upper GI endoscopy, colonoscopy, CT scans of pelvis, abdomen and chest that were all normal. I had an stress echo test that was abnormal, but a follow up angiogram was normal. Thyroid function tests were normal also. Could there be something neurological going on?