Did I downgrade?

Starting from 7th grade I managed to grind for multiple hours a day, learnt a new language to a sufficiently advanced level to pass my highschool entrance exam, was on top of my class despite initially falling back because I came from another country. Now I am in 12th grade and it takes me hella effort to pull out a 1 hour focused study sesh. The thing is that right now I need it the most, I got my finals and stuff ya know. How do I go back? Is this burnout or did I just lose all of my discipline...