Unfortunately there are no licensed medications for PoTS, so all the pharmaceutical treatments are off label and need to be prescribed by a consultant, at least initially.
If you already pay for GP appointments and tests, you would probably be better off spending your money on a prIvate PoTS specialist. Often standard Cardiologists aren’t the best, Electrophysiologists tend to be more PoTS aware and in my case I was actually diagnosed by a General Internal Medicine Consultant.
A GP should rule out other potential causes though, so full bloods to include thyroid, cortisol/adrenals, vitamin deficiencies - especially B12, Vit D, Iron and folate.
If your BP is normal, try upping your salt intake. Check the sodium levels in your hydration salts, as some aren’t great for potsies. I use PH1500 dissolvable tablets (I buy them from Amazon) since my consultant pointed out the standard sports ones I was using initially were relatively low in sodium. Salty snacks can be useful to kind of scaffold yourself if you know you are going to need to stand, salted nuts, pretzels, crisps etc. Keep a bottle of water plus electrolytes with you at all times.
Waist high compression is more effecttive than the stockings, as blood pools in the abdomen as well as extremities also the compression level needs to be quite high, my ds and I wear 20-30mmhg, which I think is the highest non-medical grade. Ideally you need to put on your compression garments before you get out of bed, as once your feet are on the floor pooling starts and you need to stop it before it starts, iyswm. Take your time getting up, wake, hydrate by sipping electrolytes, put on compression, then gradually move from lying to sitting feet up, sitting feet down then slowly stand.
Small intakes of food a day rather than large meals and cutt8ng down on carbs can help too.
Read up on pacing and spoon management, which is useful for managing your energy and also think about modifying how you do things. Eg, sitting to the table to chop veg/prepare meals. Try to keep moving over standing still if you can. I may look odd walking in circles and going up and down on my toes in shop queues, but at least I’m not fainting. Look up PoTS counter manoeuvres and try to incorporate them. Eg Clenching and unclenching fists, toes lifts, clenching buttocks! All small things on their own but they can help avoid faints and reduce horrible pre-syncope symptoms.
Have you been to the PoTS UK website? There is lots of good advice on there. Another good place for info (recommended to me by my consultant) is Dysautonomia International.
There’s a chance you may be experiencing what’s known as ‘The October Slide’ which a lot of Potsies get (the past three weeks have been awful for me symptomatically). You just recover from the heat of summer, get a couple of weeks respite in September, then your PoTS symptoms ramp up again. Lots of theories about why this happens, including a drop in Vit D, fighting off the onslaught of inevitable Autumn/Winter viruses, leaf mould, changes in air pressure, artificial heating etc. No-one really has the answer and in truth it probably varies from person to person.