Doctors and Nurses Please? Need Real Advice.?

I have a cardiac neurosis ..I have been told by doctors and nurses that im fine .no health issues but over time have developed this.I can't seem to let it go..I don't have clic heart symptoms although at different times I experience all of them more or less.I am taking meds and seeing a therapist and trying to cope..the doctors diagnosed me with depression although they knew that I had a brother that had a hidden heart condition that died 20 years ago at 44 .I have outlived him by 8 years.I am in good physical shape ,good weight,good blood pressure and strong heart and lungs clear but need reurance that its mostly in my head.i know this is a little much to ask but if you are a doctor or nurse please let me know what you think and if you need to ask further questions please contact me via email.I really need help with this and maybe someone that could tell me how to handle it would be helpful.I ask sometimes on yahoo but usually have people say go to the dr....Asking a dr or Rn plz