Welcome to HCM Forum.
From symptoms u experiencing with normal EKG and Stress Test
indicates most probably you having Panic Attacks.
This is kind of anxiety disorder usually occurs in episodes --characterised by Palpitation
numbness in limbs,coldness of extremity,dryness of mouth and impending doom.
These panic attacks usually occurs without any precipitant but can be aggrevated by stress and anxiety,extreme change of weather.
Underlying reason for this is change in chemical in the brain.
So If after thorough checkup, physician doesnt find any cardiac problem pls consult to Nearest psychiatrist
-He will definately help you to get releif from this problem