And yes it could be POTS.
Have you had a blood volume test or red cell mass study?
It should be about 25ml-35ml red blood cells per kilogram of body weight.
If your volume is say more than 15% below the minimum range, that would constitute an emergency in a case of trauma/injury, so this need to be checked.
Did you also get a 24-Hour or longer Holter ECG ?
You may want to ask the specialist to look for any irregular T-Wave pattern
specially in the downward direction from its peak where it might invert.
This, even if the voltage is fine, it may indicate left ventricle strain suggesting impaired blood flow through the aorta.
Sometimes we tend to look for a diagnosis, perhaps ignoring some significant underlying fundamentals in the process.
If positive for all the above plus an irregular heartbeat, this would be indicative of an underlying pathogenic, likely low grade, infectious condition
Feel free to post or message me directly anytime.
Note that this is not intended as a substitute for medical advice.
Wishing you well.
Niko