Do you know what triggered your POTS ? Have you ever had a head or neck injury for example ? see my post at:-
Have you noticed any particular positions, tasks, or preceding events that trigger the headaches ? Are you hypermobile ? If you can get to the root cause of your POTS, you have a better chance of dealing with it more effectively. If your joints are hypermobile, for instance, you may be suffering from slight ‘cranio-cervical instability’ (CCI). At the back-end of this one, I mention the Philadelphia collar, CCI and why you should avoid flexion:-
Can you describe your headaches – where on your head, type of pain/discomfort, how long it lasts, if anything relieves it ? You may have a few types, I certainly did. Have you had a brain MRI by any chance ?