How can I get over my fear of fast heart beat?

I started getting bad panic attacks about 2 1/2 months ago which all started cause I was having bad chest pain which caused me to have a bad panic attack and come to find out it was just gas. Well now I'm afraid of my heart beating too fast. I can't do anything strenuous or physical that will cause my heart rate to go up cause I'm afraid of getting a panic attack ontop of an already accelerated heart rate and dying from a heart attack or cardiac arrest. I literally live my life trying my best not to make my heart beat too fast. What can I do? This is making me miserable. Am I in any danger if I have a panic attack ontop of an already fast heart beat from working out or simply speed walking? I can't even do laundry barely, and I'm afraid to have ..... :(