I'm not sure what to do now

You can always take a gap year and apply to maths courses during it, if you get the grades required.

Are you not interested in studying anything related to your other subjects? You're clearly pretty good at them.

If you feel like you're struggling in maths, then retake the year because you probably can't deal with A level and AS level maths at once.If you're in a good mindset, then find a tutor and do your best this year. Going from an E to an A is not unheard of. For example, I went from an E in M3 to an A and from a low C in FP3 to an A* and from a low C in FP2 to an A, in the course of a month or two. What I did was just work harder and focused more. Things started to click after practise.

I wouldn't say I had been struggling this year in maths, I think I just freaked out majorly in the exams. I feel like my knowledge of the subject is much greater than that of an E grade student. Did you struggle with time management when preparing for the exams? Also congratulations!

Work on your exam technique. You can know the material, and suck at exams, but that is something to work on. A smart kid should be smart in everything he does, including his exam preparation and execution. My time management was basically just stay in school and practise until I got bored or the school closed for the day. Then I got a girlfriend and carried on like that, and got better a little bit until the abuse started right before the exams. I sort of have a natural ability for maths so my maths exams went sort of well, but weren't at a good time in my life. Get to the point where you know the material inside and out, and constantly work on applying it to new situations you've never tried. Feel the subject, then time management isn't an issue.That being said, there is a method you can try that's similar to preparing for an athletic performance. It's called peaking. You go really hard at revision and studying until about a week before the exam, then drop your workload to nearly zero so you can recover and rejuvenate. Then when it comes time for the exam, everything you've learnt will be popping into your head in a very calm and controlled fashion without worrying about if you missed anything. Things tend to click and become almost second nature.