I have POTS and my symptoms are dizziness, blacking out, racing heart especially in/after showers, baths, going up stairs, exertion, going up hills, dizziness when I lay down, sit up or change positions, ringing in my ears, whoosing in my ears, feeling weak and trembly and shaky. Mestinon helps my POTS a lot as does IVIG. Mine is autoimmune and part of small fiber neuropathy; autonomic dysfunction.