How is your water intake? With 3 cups of coffee and it being a diuretic, water loss could be making you tired! I notice if I don't get my 120 ounces a day I feel like crap. Experiment with this. I'm only 144 pounds and I drink 120-150 ounces per day and the days I drink more coffee and less water I feel exhausted. Our blood is comprised of 90% water so a reduction in water means more concentrated blood. A loss of only 5% water will result in a 10% loss in our blood. The blood is a vital fluid that is responsible for transporting nutrients and energy to our muscles and then transporting metabolic waste away from tissues. You could be feeling tired all the time due to a simple lack of water in your body! Give it a try for a few weeks and let me know if you see any difference!