While you cannot rule out a heart condition completely yet until you've done more tests, I'd like to assure you - if your blood, EKG and stress turned out normal, it's highly likely your heart is fine
Dizziness can be related to really many things, anxiety, low sugar level, also as a side-effect of several drugs.
I can also tell you, if you had a perforated ulcer, you wouldn't have written this message.
It's not easy but do your best to keep calm, stress is not your friend if you suffer from GERD
Just take it easy, try to eat light meals for some time and visit your GI.