why am i this tired

i used to think that maybe i slept this much because like it was winter at the time and i wasnt getting enough vitamin d or whatever so maybe thats why i was so tired all the time but like now its summer and im still unbearably tired. i had two naps today even though i had slept from 7 pm to 9 am the night before. and even after all that i still feel so tired. i sleep like 11-12 hours on average in the week, and even more on weekends. i dont know if its something medical or if my body is just getting too comfortable or something? like the second im not out and about i get extremely tired. the second i sit down to do anything, i start lulling back to sleep. but like i cant just walk around and about all the time because then i get tired too. its like the opposite of insomnia. i dont drink caffeine or alcohol i dont really have any stress issues and im pretty sure it isnt anything with my diet either since i dont eat anything crazy different from everyone else. does anyone else have problems like this? bc when i look it up on google they give me insane diagnoses.