Hello and thank you for your question! Sleepiness and tiredness may be caused by different conditions, some not harmful and other might be sign of severe coonditions that need to pay attention! The most common causes of fatigue during the day is not getting enough sleep during the night. Or the so called Sleeping apnea. In this case during your sleep, you get periods of non breathing properly. In this case the brain is not fully supplied with Oxygen during the night, thats why you fell tired during the next day. Another condition that may cause your tiredness may be Anemia. I recommend to do a Complede blood cound test, and pay attention to RBC, HgB, and haemoglobin levels. Also you have to rule out if there is any presence of Metabolism problem, like hypothyroidism. So i woul sugest a vist to your Endocrynologist. Best regards!