Going to the gym. Spondolytis too!

It's been 2 months since i go to the gym. As a child i did swimming for 9 years from class 1 to class 9. I played football. Then 2 years badminton. I am 23. Now for 2-years in beetween i became very less active but now again i have stated work out and going to the gym. But when sometimes i see gym videos of people collapsic or having cardiac arrest i panic. Then at the gym whenever i have slightest pain on the left chest or any acidity i panic and leave the exeecise. In this fear i did my ecg and echo cardio and the doctor said i have a perfect heart. "His words" so should i be worried and worry about my physical exertion. Cause this age is about being free and exercising. I have cervical spondolytis too