LMAOOO same I'm garbage at general maths, literally have no mathematical ability whatsoever
I think it's just the nature of your personality, you're just like, bomb af at English and other essay-based subjects but when it comes to maths I'm scraping Band 4s, it might sound really dumb but despite past papers after past papers, like me, you would think we'd have confidence going into an exam, I mean yeah general maths should be a simple subject and at first you understand it but when the exam comes you interpret as it would be a past paper question, thinking you're doing it right but realistically you're using the wrong formula or you can't approach the question because you don't know how to answer it.
In this case, I think despite the marks and the associating disappointment, you still just need to do past papers, chapter reviews and do the difficult questions that might be in the test, it's like low risk low reward for people like us, but if you have the right mindset and approach the exam with relative confidence, then maybe, just maybe, you'll finally be happy with an exam result.
Also your ranking is 14/16, which is not necessarily a bad thing because it means your cohort is strong (or maybe just because it's genny maths but whatever lol), 13 other students performed well in their exams which indicates that it's not necessarily the exam that's the problem, it could just be that you find it difficult to approach mathematical equations and concepts say compared to English, where you can just write whatever you want, whereas in maths you gotta get straight to the point and answer the bloody question.
TLDR; don't be too disappointed in your mathematical performance, I'm in the exact same situation you, good at everything else but bad at maths lol, you could ask to see other students' exams and see how they approached their questions and you could compare with yours and why you're getting the questions wrong, good luck though!!!