Extra time

I'm currently doing my A2 exams and am getting very stressed after my exams as I can NEVER finish an exam.

I've been having this problem since GCSE's, with the exception of GCSE maths which I never had problems with, so I’ve realised it’s just written exams I struggle with. The problem has gotten much worse during A Levels as I do 4 essay subjects. I’ve always moaned to teachers I struggle with timing and whenever I get mock results back they nag me about my time management as I always leave questions out/largely unfinished as I run out of time.

Aside of this, my writing quality is pretty good when it’s not timed conditions, but as soon as I’m in an exam I completely lose sense of vocabulary/structure/quantity etc and can’t write enough in the time. Teachers have always told me it's because I haven't 'revised enough' when I get mock results back. However, this year I've worked so hard going over and redoing my notes almost every day after school all year, and revising since February/March. I know the content SO well for my subjects, I just cannot express my knowledge in timed conditions at all.

I’m not a slow writer (which is why people I know get extra time), I just can't read a question, process it, think of ideas and put pen to paper quick enough, and it’s really ****ed me over in my A2 exams this year.

If I’ve messed up as badly as I think I have and have to resit next year, will I be eligible for extra time if I finally get a teacher to take me seriously?