I do have POTS in fact. Always had it. I was just re-tested January 4th, 2018 and it confirmed for the 3rd time a 30+ BPM increase in HR when elevated.
The test I had last september that made it look like I didn’t have it wasn’t done properly, because they only have me in the supine position for 10 seconds before the elevated me right up, and I was elevated before the test.