Sunsetnan

I had the same symptoms, heart palp., flushing, diarrhea, nausea, sensitivity to noises, and sounds and blood pressure spikes. I was tested for hyperthyroid, pheochromocytoma, carcinoid syndrome, etc.. All came back normal. Turned out that I had severe reactive hypoglycemia and my fibromyalgia had flared.

As I understand it, my sympathetic nervous system (fight or flight) was in overdrive from drinking caffeinated beverages, taking stimulants in the form of decongestants, dieting, exercise, and stress. And, most likely because I stopped taking my SSRI that helps the autonomic nervous system keep Serotonin in the brain. If I ate something with starches or sugar, then my jazzed up nervous system would over-secrete insulin and my blood sugar would plummet 3 hours later. That low blood sugar would cause my jazzed nervous system to over secrete adrenaline, and my blood pressure would spike. Crazy!

I had to get everything under control by avoiding caffeine, stimulants, sugar, flour, corn, and higher GI carbs (few fruits). I now eat a hi protein, very low carb diet and take a beta blocker. My blood pressure is now normal. I had to start on an anti-anxiety medication to help with the effects of the excess adrenaline until it improved. I also took a stress reduction class and try to meditate to get my parasympathetic nervous system (relaxing) to be more dominant.

The hypoglycemia was diagnosed with a six hour glucose tolerance test. My blood sugar at hour 3 was only 24! The doctor said I should have been in a coma. I would check this out in your case. You can try to see what you ate and when at the time this happens. You can also make sure you eat small frequent meals and avoid sugar and carbs. Be patient. It took quite a while to get everything back to near normal. I still have to eat every couple of hours to avoid my blood sugar from getting too low and I have to look at labels to avoid hidden sugars.
Hope this helps,