I have similar experience, I used to be able to run a lot before POTS! Very very slowly I have been able to get back to some jogging but I can’t run fast anymore without getting extremely dizzy or blacking out. However I have been able to run long distances again at like a 13 minute mile pace! Way way slower than I used to be, but this is a pace I can sustain for a longer time. My tip would be to start with slow jogging like that. I know how discouraging it can feel :( but there is hope!! Remember that on the days that don’t go well! It’s a long process. You can do it!!