Chilling Sensation. What this could be?

Hi Doctors, I am suffering from gas issues from which sometimes i used to get pinch time pain in chest. From which I really got anxious and started to think that i might get heart attack. To rule this out i did ECG which came normal. 1 fine day i was on my way back home after office around 8 and while driving i got chilling sensation which started from chest and spread out to the whole body and followed by shortness of breath, I didn't stop i my rushed to nearest multispecaility hospital and they did my ECG it came out normal. Still i was in doubt that I might have got silent heart attack to rule out that doubt they suggested me to go for troponin blood test which came negative. My question is when i feel like pooping i get that slight chilling sensation and when i stand and walk around it subsides. Though the chilling later burning sensations doesn't spread out to body like the first time. What this could be?