Hi
First of all, I'm autistic with ADHD, so I have been where you are now. It sounds like you are experiencing autistic burnout. The transition between GCSEs and A levels can be a difficult one as there is quite a jump in workload and challenge. When we start to burnout everything gets really overwhelming. This can make our anxiety and any sensory issues worse. I spend a lot of time in my home studying right now and I find that when I go out my tolerance for noise, people, lights etc is lower now which you probably noticed too post lockdown.
Is your school aware that you are autistic? Do you have a PLP or any reasonable adjustments in place? You need to speak with someone in pastoral care, and get a parent, sibling, or friend to help advocate for you at this stage and go along with you to a meeting.
I think that dropping from 4 to 3 subjects is a smart move. It may also be possible to retake a year or to spread your A levels over 3 years. If you are struggling then it is up to your school to make sure that your needs are met. By talking to someone, or, if you are like me, by writing something down, you might be able to start to identify what you need. In an ideal world what would really help you right now? Start from there and write it or record it, or map it or draw it. Work with your brain in a way that is most comfortable.
Would it help to have a laptop with Dragon, so that you could speak your essays? Would software that reads to you help? Do you need timeout during the day to spend in a quiet place by yourself? Can you use noise cancelling headphones in the classroom? Would it help to have some sort of work buddy? Would hybrid study help? You might be able to reduce the number of hours that you spend in school or college, for example. As autistic people we might need support to create an environment and situation that works for us and our brains. It is up to our schools and places of education to help with this.
I am sorry you are feeling hopeless and lost. It's a horrid place to be in and I completely understand. Please seek out some support. If I can help with any other questions, please let me know.
In solidarity
Sarah