Maybe look into PoTS? If it is pots or that sounds right and it's getting really bad, try electrolyte drinks and lots of rehydration, as well as increased salt intake.

Also look up panic attacks. Some of those techniques can be helpful. For me, food wise, low histamine and low sugar, high salt, low fat. Check with doc first about the salt if you have high blood pressure. If you do have high blood pressure, metoprolol may be a good choice. A lot of people reports that it helps them. For me, spironolactone + metoprolol stopped most of the episodic attacksm