Hello and welcome. I think you are right on track by having a Holter Monitor as that should help your physician identify any heart arrythmias when you are having an episode of chest pain.
Please do not be afraid to call or present to the ER if you chest pain changes or you have any sx.
Here is a list of the warning signs and sx of a heart attack:
Uncomfortable pressure, fullness, squeezing or pain in the center of the chest lasting more than a few minutes.
Pain spreading to the shoulders, neck or arms. The pain may be mild to intense. It may feel like pressure, tightness, burning, or heavy weight. It may be located in the chest, upper abdomen, neck, jaw, or inside the arms or shoulders.
Chest discomfort with lightheadedness, fainting, sweating, nausea or shortness of breath.
Anxiety, nervousness and/or cold, sweaty skin.
Paleness or pallor.
Increased or irregular heart rate.
Feeling of impending doom. Reference: American Heart Association
Not all of these signs occur in every attack. Sometimes they go away and return.
Many other things cause chest pain also. Anxiety and GERD are a couple that come to mind.
Please do keep us posted.