Always tired. I am not sure what blood work was done but make sure that epstein barr virus was included and if you are male that a testosterone profile is included. Usually is it is not the quantity of sleep but the quality. One thing to be consider if you are experiencing sleep apnea. Adding energy drinks to help may worsen the situation due to their high content of stimulant that cause fatigue hours later.
Good question. Tired or fatigue are non-specific symptoms of a large number of maladies. Not getting adequate quality sleep is common cause; anemia, underactive thyroid gland are just two which lab tests should pick up. A viral illness can cause it but should resolve by 3weeks. If you fall asleep during the day, you may have sleep apnea & not know it. Underlying depression, another. So if goes on >1month, c gp.
Depression? Depression can be another reason for feeling tired all the time. The classic symptoms of depression are decreased energy, motivation, and interest in usual activities or hobbies with depressed mood. Most energy drinks contain caffeine and sugar which hype you up for a few hours and then you "crash" and feel tired and apathetic.