Hi Rachel,
My daughter has recently been diagnosed with Autonomic Dysfunction (dysautonomia) and has similiar symptoms. I found a link between gluten/other food intolerances and dysautonomia which is what lead us to this diagnosis. Unfortunately I no longer have that link but am sending another that provides general info on the various forms of dysautonomias.

http://www.potsplace.com/index.html

My daughter got her diagnosis from a cardiologist via a tilt table test and a 24 hour holter and will be traveling to the Mayo Clinic next month for further diagnostics.
Hope you are feeling better today,
Lisa