What Causes Severe Fatigue And Loss Of Appetite Of A 2 Year Old?

Hi. I have a 2 year old boy. He is starting to sleep alot lately and not eating as much and seems to be getting tired quick. I have read stone forums that say to check if he remembers what he did that day like showing him the same pictures as earlier or play a game what he played earlier and everything seems to be fine he remembers it all should I be worried about it and consult my doctor tomorrow or do you have a different answer for me??. Thanks David.