Hi I feel light headed everytime I eat + other feelings that have been very scary!!

Hi I feel light headed after I eat any meal light or heavy or healthy. I just turned 31 and ive gone to the ER 3 times in the last 6 months, it all starts with a stomach pain I go to the bathroom I feel like vomiting and a throbing head ache takes over followed by my heart beat racing fast, I feel as if I am gonna pass out or die!! And saliva starts to decrees to the point I have none. Everytime I go to the ER they check my heart with a machine they do blood work blood presure sugar levals and find nothing!! It is very stressfull to no something must be wrong but the doctors find nothing... Someone please help this is very scary!!! I feel like im going to die!!!!