On fludrocortisone for pots. if my body stopped producing as much natural aldosterone due to the steroid, will it still throw out excess potassium?

Yes: Fludrocortisone is a drug that has effects similar to the natural steroid hormone aldosterone - it acts to preserve sodium(Na) and increase water retention, and at the same time increase potassium elimination (K). Usually taking fludrocortisone suppresses your body's aldosterone, but it leads to more K losses, because of the aldosterone-like effects.