You may find help from the
http://www.medhelp.org/forums/Undiagnosed-Symptoms/show/95
I think it worth a try, just cut and paste - while we try not to double post I think your issues may find help in a couple of places... not a one subject issue.
You may get some help here are anxiety related to your type of situation, and it may be that anxiety can contribute to dizziness..I don't know, seems your doctors are trying that approach and treating anxiety/depression.
How is your heart? Your blood pressure, your heart rate, you oxygen saturation levels? I'm sure your doctors have checked all these when you are in the office, but you may need a longer term monitor. Most of us with heat problems just check our own HR/BP, even some, me, check our oxygen saturation level. The heart rate can be checked with a watch and fingers, the blood pressure either by a home device or at the pharmacy every time you in to one. An Oximeter is not expensive to own as well.
Dizziness is a classic symptom of heart problems...the brain isn't getting enough oxygen.