i'm fucked (vent! tw: eating disorder)

i'm sure i'll fail that school year bcs of how much classes i missed for being to depressed to get out of bed. My twin brother is in the same school year as me and tried to help me a lot (really, he's such a good and helpfull person and has been the only  one in my family trying support me, he is a little distant/cold towards me and don't talk to me a lot but i just love him so much!), i am fast at learning so i did great in most of the subjects thanks him, but in the subjects i've always find more difficult to learn and really can't understand i ended up  just copying the ansewrs he was giving to me while we did our exams bc my stupid tired brain don't work as well as it used to do in consequence of all of my other mental illness, lack of proper nutrition and other health conditions. Due to my eating disorder i'm always so tired and can't really focus on anything, i have a really hard time reading now too. My mom talked to the principal so i would do some extra projects with my brother's help to get some extra credit like i did least year but she said that the school couldn't do that and the only reason they did it last year was bc i was away from school to have mental health treatment. I'm really so angry at myself, i have problems for sure but they shouldn't affect that much, i was supposed to be smart and not having any problem learning like i always did , i feel like such a failure, the only quality i had is slowly fading away. I keep telling myself that i'm not so sick and i'm just gonna "ruin my future" (it's to dramatic to say having to go to school for one + year than everyone at my age to catch up them will ruin my future but my brain is a drama queen ok) bcs i didn't worked hard enough or wasn't good enough.