I have had diarrhea almost every other day for as long as I can remember. I also feel constantly tired and out of energy. Whats wrong with me?

Need evaluation. Could be parasites, celiac sprue, infection, inflammation, tumor, iron deficiency, anemia, other stuff. Need to see your doctor.
Many things. Chronic diarrhea can lead to dehydration/volume depletion, electrolyte imbalance and porr nutrition all of which can lead to fatigue and lethargy. A thorough workup, identifying the cause and proper treatment once the diagnosis is made can significantly improve or resolve your problem. See a colorectal surgeon or gastroenterologist for a thorough evaluation.
Not clear. You need a full evaluation, as there are many possibilities. A colorectal or endoscopic surgeon, or gastrenterologist should be able to help you.