POTS is still considered a new medical term having only been recognised within the last 30 years. As @Celandine
has said there are a lot of treatments and loss of physical functioning assistance available.
I’m not very surprised your GP is misinformed about it. I think you should try to test yourself as suggested. This would be life changing support you are missing out on if it is the case that you do infact have POTS.
The other posts you have made suggest you may have some form of exercise intolerance, and that’s what is limiting you in being able to walk for long periods.
The NHS says POTS is common in people with CFS
One of the symptoms of POTS is exercise intolerance.
Exercise intolerance is associated with an onslaught other symptoms which make you feel poorly. Of course, you may not have exertion/exercise intolerance but the only way to be sure is through physical examination.
What may be helpful is if you write down all of the symptoms you have ever experienced since falling ill with cfs even before diagnosis. Then matching your symptoms with other people diagnosed with POTS and the ones mentioned within various sources. It’s a neurological disorder so everyone’s symptoms will vary and symptoms may appear unrelated as Dysautonomia and POTS dysautonomia affects multiple parts of the body. Many differing symptoms is a hallmark of autonomic dysfunction.
I want to add it would be highly unlikely that CBT and GET will work unless any underlying physical conditions are addressed. The GET and CBT programme is based on the patient being deconditioned and not physically ill.