Maria, I’m so sorry to hear you had such a horrible night! That had to be really scary. Since you’re at home right now, do either of your parents have a blood pressure cuff? You could check your BP during those events to see if your pressure has dropped during that time.

This entire situation you’re going through is way out of my level of experience. But years ago I did have heart palpitations and a doctor gave me a way to reset my rhythm. I looked through some articles this morning and found this one which gives pretty simple and clear ides for how to calm the palpitations. It’s not from a medical source and it’s not a permanent fix. But it helps to regulate beats when you’re having an episode.
https://www.besthealthmag.ca/list/natural-home-remedies-palpitations/#:~:text=Like%20the%20Valsalva%20maneuver%2C%20coughing%20increases%20pressure%20inside,this%20helps%2C%20but%20some%20people%20get%20instant%20results.
From my understanding POTS is positional and generally happens when a person is standing. So it’s curious that you felt the same feelings when you were lying down. Honestly Maria, if this happens again, it might warrant another trip back to the ER. I know you’re visiting and in a foreign country where your insurance doesn’t cover anything but emergency. But if your heart is at risk that IS an emergency.

How are you feeling right now? Did the symptoms pass?