[9V-SIA]

The symptoms you describe most certainly are more severe than IBS.
While your EKG was normal, I would go for a CT angiogram of your heart just for peace of mind.
Many of my colleagues had normal EKGs but abnormal CT angios.
Heard of unstable angina? That sounds like what you had.

You should check your heart especially if you have:
family history of heart disease
high cholesterol
hypertension
diabetes
smoker