Help? Why do I feel my heart beat faster at night or is it anxiety?

It’s new feeling I felt since yesterday, like it’ll be midnight I’m laying in bed getting ready to sleep, and I feel calm as I’m relaxed but my heart feels weird like I feel the pounding. Or am I confusing it with maybe heartburn in the chest? I have severe acid reflux , I used to feel popping in my stomach now I feel it in my chest. I also get chest pains but rarely if I eat spicy or greasy food.
Help? Why do I feel my heart beat faster at night or is it anxiety?
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