Why am I feel so rundown?

ok so basically I am a person who is used to doing a lot of stuff but recently I don’t know I have just been so tired and I dont want to do anything. like I get home from school and I crash in my bed or I will get on my laptop…and crash in my bed…I cant focus on anything like during one test I took the song frosty the snowman was stuck in my head or the littlest thing will distract me sadly like the celing which really isnt that interesting and its not just during school its 24-7. the sleep I do getis very little during the night(typically during 4-6 am) but I sleep at other times… I am big on energy drinks when I dont sleep but I dont drink them everyday its like 1 every few weeks or 5 within 2 days when I am seriously cramming or desperately need energy. I dont have the desire to do anything that I love to do and for a week I didnt eat because I wasnt hungry and I didnt feel like it..I mean I forced myself to eat more recently but everything just seems to be coming to a standstill and a lot of things either bug me or I dont care at all. can anyone tell whats wrong with me? lots of advice needed