Hello.... You did not mention your age. There are two things...Sometimes Panic attack per se can cause chest pain and palpitation. But sometimes if any one having some previous heart pathology then sudden mental stress can cause chest pain due to vasospasm of coronary artery disease called Unstable angina. As you said, your doctore done your ECG and blood test that came neagtive for any heart pathology. So it may be due to panic attack you are feeling chest pain. In that case, nothing to worry about your chest pain regarding your heart but you have to control your anxiety and do some life style modification with some yoga for piece of mind. Thank You.