dropping out of y13 and restarting?

im not quite sure how to word this since i am feeling a bit erratic currently however its coming very close to the real alevel exams and i am so severely underprepared. im predicted a*aa however my mental health has been so awful that my attendance is 30% currently and i have absolutely no faith in myself to catchup. i was wondering if it would be worth dropping out of y13 as of now and then retaking the year & alevel exams next school year. im just really scared as ive been accepted into uni of manchester and ucl so my family is very excited for me to start uni at somewhere so prestigious and im scared that if i were to retake, these unis wouldn’t even bother looking at my application as i know retakes are not favoured. im really stressed as i do want to retake however im not sure ill get into a desirable uni if i do. ucl and manchester want aaa and as of right now i dont feel capable whatsoever, my insurance wants abb and to be totally honest that doesn’t even feel achievable either. i got bbc in my last mocks and i just feel very disappointed in how this year turned out as i had high hopes and expectations for myself. sorry this is so horrible written it’s 3am and im stressing so immensely over this