Hi, Drinking 3 cups of coffee and energy drink is containing too much caffeine, which is over-stimulating your nervous system. Thus, your heartbeats are increased and you had a feeling of fainting as reaction. The very first thing I advise is to avoid/limit coffee/energetic or other caffeine rich drinks/foods until improvement. Your body does not need such high energy level as it has its own energy-regulating system. Next, I d ask to measure your blood pressure/sugar levels, record the results for future reference. Hypoglycemia could be another cause, however, monitoring of blood sugar would determine it. Hope it was of help! Dr.Albana