welcome to healthcare magic forum
help you reduce stress? Or it made you worry more and more about you health, to the point you are have a an acutal FEAR of DEATH. I hope you stick to your decision of quitting the habit permanently.
Shortness of breath
attack indicate that you are going through mental stress. You may see a psychitirst or a homoepath for this, for medicines along with some talk. This will help a lot.
For your fear of death..you may see a physician for an examination & test , so you will get to know (for sure) whats going on inside the body. Hopefully this will give you confidence and motivation to lead a healthier life.