There are a variety of causes of the feeling "stomach spasm", including ulcers, inflammation of the upper digestive tract, irritable bowel syndrome or GERD. Certainly stress can exacerbate these symptoms, but should be considered when the organic causes have been ruled out. I would consider an upper GI series or upper endoscopy (which is the more comprehsive test) for further evaluation. A blood test for H Pylori - a bacteria associated with inflammation or ulcers - should also be considered.
Regarding the palpatations, you can consider an event monitor or echocardiogram to ensure that a heart condition isn't the culprit. A thyroid test should also be considered. You may want to discuss these options with your personal physician.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Thanks,
Kevin, M.D.