Experiencing full body paresthesia symptoms late in the day/at night only. Could this be a cortisol problem? Other possibilities?

Easy to find out. Have an AM cortisol level checked as well as calcium level drawn. Discuss your parasthesias with your doctor. Induced acid base disturbances (hyperventilation and medication use) can affect calcium binding and produce total body parasthesias. This usually resolves with CO2 capture through re-breathing (eg. using a small paper bag) if it is due to hyperventilation (breathing too fast or too deep)