This patient support community is for discussions relating to Dysautonomia (Autonomic Dysfunction) including: Postural orthostatic tachycardia syndrome (POTS), neurocardiogenic syncope, mitral valve prolapse dysautonomia, pure autonomic failure, autonomic instability and others.
I guess what I'm trying to say is that it is worth a shot. It isn't going to be a total cure, but there is a decent chance it will bring a more stable backdrop to your body. I know that my "hydration level" tends to fluxuate a lot on its own, and fludro helps me get to a more steady state (with less overall drinking & peeing in my case).
If you have what looks like chronic low blood volume, like dehydration symptoms much of the time, then fludro is a "first line" thing to try... if your BP is high, maybe it's not... check closely with your doc.
I think AireScottie is right to mention autoimmune issues since those can zap the thyroid along with other things and might be a root explanation... worth considering.
If you're in the position of looking for possible other culprits for your symptoms that are less positionally-dependent but otherwise similar in presentation to POTS, one thing that ought to be ruled out is pheochromocytoma if it hasn't been already. Mastocytocis/MCAD also ought to be ruled out. Depending on your particular constellation of symptoms, there may be other possibilities.
If you're not in that boat, then it still sounds like you need to find a good doctor to oversee your POTS treatment. Where did you get diagnosed? Why isn't that doctor continuing as your treating physician for your POTS? Who is currently prescribing the beta blocker? If you need to find a new POTS doc, I would recommend an EP cardiologist as others have above, if you can find one with knowledge of dysautonomia/POTS.
Without knowing more about your signs/symptoms, it's hard to say much more. Do you have tilt table results? What are your BPs (lying/sitting/standing)? And your HRs (lying, sitting, standing)? Do you have syncope, and if so, how often? If you have syncope, what happens when you faint (orthostatic hypotension, bradycardia, tachycardia, asystole, flutter, fibrillation)? You mention anxiety, sweating, fatigue, loss of appetite ... what other symptoms do you have and which are triggered by position, exercise, or heat and which are chronic? Do you have other health conditions as well that have to be taken into consideration?
Perhaps knowing a little more about your situation I will have more insight into why your doctor started you off with just a beta blocker rather than one or more of the other POTS meds.