What Causes Dizziness While Having Normal Blood Pressure?

Dizzy when just standing. I am 36 year old female and I have these spells, I get flushed, nauseous, my legs feel weak and my head feels like it is buzzing. Foods do not seem to help and I am adequately hydrated. I also get it when I walk even short distances. I was tested for BPPV and Meneires and both were negative. There was also no sign of an inner ear infection. My thyroid is good, it was hyper but has since returned to normal, for over 3 months, just recently rechecked. EKG was fine. BP has been between 106-120 over 60-80. Pulse around 75-95.