Well you are lucky that doctors have not been able to find anything because tumors and other cancers are easily diagnosed.
But of course you cannot blame the doctors that they could not diagnose anxiety, because they themselves do not know why people have anxiety attacks. You need to study clinical nutrition for this.
I suggest you read some articles at our web site at:
Hypoglycemia.Asn.Au
"what is hypoglycemia?"
"beating anxiety"
"hypochondria and hypoglycemia"
"depression a disease of energy production"
"depression a nutritional disorder"
once you have read all of the above article you should know that your 'disease' is easily treated by a change in diet.
Jurriaan plesman, ba (psych) post grad dip clin nutr