YA novel where socially awkward boy who is also an outcast writes about his classmates in a journal & then he has a glow up & starts getting popular. he also kindles a sort of romance with a popular girl & his journal gets leaked

[Autumn]

I read this book around 2022-2023 in highschool?? Our library had it. I just remember it was this socially awkward teen boy in highschool who also wasn't too popular but he didn't particularly care. I think his sister was older & used to go to the same school & she was popular & would sort of protect him. Then he cuts his hair & has like a huge glow up. He'd also write about people in a journal & then it gets leaked. He had something going on with a popular girl, she was nice.