This is my understanding of the disease. You also might have orthostatic hypotension, which is a decrease in blood pressure when you go from a sitting position to a standing one, usually caused by dilation of the blood vessels. Most people who have this usually feel light headed when they stand up. To compensate for the drop in blood pressure, what your body does is it speeds up the heart (tachycardia) to try and pump more blood out, which will increase your blood pressure. Now your blood pressure is fine, but the problem now is that your heart rate is through the roof.. now you have orthostatic tachycardia.
There are A LOT of vasocontrictors that exist that would stop the hypotension from occuring. Your right in saying that adderall may be helpful, but i don't think it is 1st line treatment due to the dependence factor and there are alot of other drug options out there that are just as effective that don't have that risk factor. You'll prolly get something like fludrocortisone (a corticosteroid) or midodrine (an adrenergic alpha-1 agonist).
Either way, hopefully either of those medications work out for ya if u choose to take them. Best of luck!
-cap