I really hope things improve for you. I just read about POTS. Sounds unpleasant at best.
I used to have PSVT (paroxysmal supraventricular tachycardia) which is an arrhythmia caused by a short circuit in rhe hearts electrical wiring. It caused my heart to start beating at 200 BPM which is so fast that my heart couldn't fill with blood between beats and my blood pressure would drop to 70/50. Couldn't even stand up and walk during an episode without passing out and it would do it for a full day sometimes. They did an ablation procedure a few years ago and fixed it- never came back. I think POTS cause is more complex and can't be fixed with ablation.