What you have described in your last post is very suggestive for panic attack.
You were doing nothing stressful, and, yes, that's the way these episodes come, abruptly and without prediction and obvious triggers.
People that are experiencing panic attack for the first time, usually, fear that something very serious is happening.
Being afraid of dying and afraid of being alone, are another characteristics of panic attack.
On the other side, chest pains can be really a symptom of GERD.
This kind of pains can also mimic pains due to heart problems.
Blood hypertension monitor will give an answer if you have a white coat syndrome.
Do you usually worry for not being able to fall asleep, leading to heart pounding, palpitations and chest pains, when lying in your bed?