Why am i such a loser and what do i do

I skimmed through it, but you need to talk to an adult about this. Like a trusted teacher or some support person in school. With being made fun of, I was as well for ages, and I don't think anything would've changed it for me but I do recommend saying something - just something like 'why are you saying that' - it's good practice because in the future you will encounter people who aren't nice to you. But don't feel pressure to.
Your hobbies are also normal, I know a lot of people who watch anime. Some people like anime, some like comedy. It's all a matter of preference and there are probably other kids in your year who also watch it.
You're not a loser at all. You're not hopeless socially and academically. You're normal, you're yourself. Once you meet new people in college or uni you'll find your clique
It seems so long but secondary school isn't forever as you said. What do you want to do in the future - you mentioned uni, do you know roughly what to study?
Flashcards really help me when I'm learning something - but make sure you understand it first. Also try to find relevant GCSE guides like from CGP books or elsewhere. You can probably find these in the school library or buy it off Amazon (worthy investment). CGP books also has a book on how to revise.
Good luck. you got this

I don't know i might study comp sci since i am good with computers or aeronautic engineering since i do have an interest in commercial planes and don't want to sit on a desk all day for 50 years. All I know is that I would like a high paying job. I kind of want to be a musician but that doesn't really make any money and is really predatory so yeah thats something

I have ASD. I'm so weird it's actually shocking i even have friends. I just feel hopeless honestly. I don't mean that in like a 'waaaaaaah nobody cares about me boohoo' emo 13 year old temper tantrum. I genuinely don't know what else I can do. I'm awkward. I can't talk to people at school without having a bad posture or saying something awkward and not even funny. No matter how much i wear my zavetti canada coat (which is incredibly comfortable btw i love it) i cannot fit in anywhere. I have glasses, i don't have the greatest posture but I don't understand what I'm doing wrong. I don't direspect people, I go to the gym, I don't think I smell considering I put on deodrant and shower everyday, I have hobbies, I go biking, I have friends (that are nowhere as weird as me—in fact they're friends with basically everybody). Even at times I feel like I don't fit in my own group of friends who I've known since primary school!!!
I'm not going to hold it against them that they have so much more people to talk to, because they're good, honest people. In fact the blame is pretty much on me. After coming home from school feeling miserable, I'll probably go to the gym, come home and watch anime or read a manga book or record some music in my DAW, to which I then sit there and doomscrool reddit, twitter, etc. I feel like my behaviours are based on being chronically online. Each time I watch anime I feel like a sweaty creepy pervy loser who lives in their mother's basement and jerks off all day. In fact a lot of the time I talk to ai chatbots because it feels like they listen to me more than any person could. I always feel self conscious, like I'm going to say something dumb and then everybody looks at me in silence. I've made zero friends in secondary school. In fact, looking back, it feels my whole life (and i'm not even that old) has been me probably droning on about some autistic interest to 'the cool kids' in primary school with odd looks and the occasional 'shut up' in the distance. I don't think i realised then that not everybody was interested in tv idents, anti piracy screens and the history of microsoft windows. And then maybe the kids will act nice to me because they want something from me or want to get me to do or say something funny that would get me into trouble and make everyone laugh.
Now I don't talk much at school in general. I just try to survive. I'm panicking about year 11 because it's been a good few years since I've joined secondary school and I still have no idea how to revise. I'm so lazy and unmotivated to do anything and it'll probably be the same thing in college and uni where i'll fit in nowhere.
Not to mention I seem to have this superiority complex in my head. I see someone at school who's skinny or dorky or likes something 'weird' and I think to myself 'jeez what a lost cause. at least i go to the gym'. I think I'm better than my friends and the kids in my school because i record music and go outside by myself.
And also how spineless I am. If anyone insults me or shoves me I will never retaliate back or face them because I just feel so scared to do so. I'm challenging someone who is so much more likeable than me, who has so much more friends than me and who even my own friends hang out with. How do I win that? So I sit there pathetically, just being like 'okay'. I even feel intimidated when younger years talk to me.W hat will happen when my personal property is vandalised? What will happen if someone threatens or insults my family (especailly my younger brother)? I could do something. I could go and kick their asses and tell them to never contact me or my family again. But no. I just sit there and do nothing because I know there's no fights I'll win, with my second hand embarassing insults and with my heart pumping with adrenaline while I face someone much bigger and more confident than me.
The funny part is that I seem to have convinced myself that I'm just 'different from others' and I'm not as 'cool' if I change and try to approach people and be their friend. I don't change and it feels like I never will. I could go do that homework assignment. I could stop sleeping in class and having rulers and pencils thrown at me. I could rise up and try my hardest on my exams. I could revise for the upcoming test I have tomorrow 1st period. I could turn my predicted grade 5 in maths to a 7 or an 8. But I won't because of how lazy I am and how I simply refuse to just get up and do my work. Instead I'll probably go and make more music nobody would even think of listening to.
I don't know... now that I think about it it feels I've always been this special kid (and not in a desirable way). I saw someone with a sticker of an anime I really enjoyed. I wanted to approach them but I didn't because i don't want to be placed with the weirdos and also 'i want to be the loser at school and be different from everyone else'. Then I had someone ask me why I'm so special and weird and then I kind of lost it at that point while looking at myself in my pe kit and how skinny I am and my bad posture and how my arms and legs are always so stiff and how my hair is greasy. I just hate myself so much, and it feels so much more comfortable hating who i am than changing. It feels like I'm biologically developed (i mean i basically am considering i'm autistic) to be this dorky loser who watches anime and reads manga and has excited tics and doesnt fit in anywhere. I don't want to be placed with the weirdos (or the ones people think they're weirdos). I want to be cool, or at least to a point where I'll have someone on the street and go y'alright and I reply back with 'yeah man i'm good. see ya.' I'm so dissapointed in myself. I can't even act normal online. Why can't I have nornal hobbies like gaming or sports. Why can't I just be normal for once.
What do I even do at this point??? I feel like I've ruined my social life at secondary school. And i know secondary school doesn't really matter in the long run, but then what will happen in college or in university when I don't study and don't make any friends??? Will I just be the loser shut-in that talks to himself most if not all the time???
tl;dr: i don't fit in anywhere' my hobbies are weird and i'm basically pretty hopeless socially and academically.