Usually, a worry about heart attacks brings adaptive response of engaging in health promoting behaviors like exercising regularly, keeping healthy diet etc. However, in your case, this worry about heart attack has initiated a series of behaviors that are opposite of health promoting behaviors.
Basically, your relationship with your bodily sensations, specifically sensations related to heart like palpitations, aches and pains, breathlessness, etc, has distorted.
May be there was some event which specifically initiated this severe anxiety, which mimicked a heart attack (as per your knowledge of heart attacks).
Hence, the cognitive behavior therapy sessions help you get back to feel comfortable with those sensations.
Next Steps
book an appointment with a clinical psychologist
Health Tips
next time you have sensations which you don't want to to have you just sit down down for 15 minutes and do nothing. observe how it goes on its own. observe how your thoughts goes on its own.
my best wishes