@azurite I don't have POTS (Postural orthostatic tachycardia syndrome), but have a some of the symptoms. My bp tends to be low and my heart beats fast for no reason at times. I think diet is one of the main things that is going to help you. Sodium helps... salty foods and not eating many processed foods. You could take salt tablets. I haven't done that yet. Instead of 4 meals a day divide the food into 4-5 meals.

I did a very quick search and these are good articles. I saw there are some videos on youtube that might be worth watching too.
https://my.clevelandclinic.org/health/diseases/16560-postural-orthostatic-tachycardia-syndrome-pots
https://newsnetwork.mayoclinic.org/discussion/mayo-clinic-q-and-a-all-about-pots-postural-tachycardia-syndrome/
I am sure there are more post on this site regarding the subject. ... if you haven't tried the search option at top of page try it... try POTS and if no results try full term of Postural orthostatic tachycardia syndrome.

Zee Gee