I hate postural orthostatic tachycardia syndrome! I wish there was more research for what seems to be unknown illness from many doctors :- (it affects more than just heart :- (this is a plea from many?

Electrophysiology . Did you get checked by cardiologist specializing in electrophysiology ?
Sympathize with you. Yes, pots can be difficult to treat but more research is being done and there are more treatment options. Have you seen a pots specialist? You want a doctor to look at the underlying issues (the root of the problem) and not just the symptoms (the tachycardia). Pots can be caused by many different things. It is a syndrome and not a disease. You should seek help to figure out what is causing it.
Listen to your body. Biaxin (clarithromycin) and Nadolol are not helpful for pots. Eating 6 equal healthy meals with fresh vegetables, fruit, high quality protein, essential fatty acids, unprocessed sea salt, coconut water for electolytes rather than just water, relaxation breathing for 5 minutes, 10 minutes of core exercises lying down, after each of these 6 meals will gradually restore you to resiliency. See kelly mcgonigal.