After reading your history, it appears that you may be suffering from a psychiatric disorder.
As you have mentioned you are 29 year old , so it's very likely that your heart must be working fine. Also you have already investigated yourself few times and every time it came out to be normal.
Keeping your medical finding being normal and your persistent worry about having a disease , you may be suffering from hypochondriasis
For a confirmed diagnosis you should get your self evaluated by a psychiatrist
and get your diagnosis
Once diagnosed you may be advised psychotherapy
and if needed then some medication.
You should compile to the treatment for best outcome and this will prevent you from lending in emergency every now and then for your cardiac work up and you may be able to live a happy and calm life