CHI0059
Howdy, QCE student here so idk how good I am at giving advice.
I suggested you do topic tests for each topic in each subject. That way you'll find your weak spots. Once you've fixed up your weak spots, start doing practice papers. Because there's only 3-4 weeks left, you might have to accelerate this process. Then mark your practice papers, go back and revise stuff you're not clear on, and do another practice paper. Rinse and repeat.
Create a timetable to schedule in when you'll do these tests, it'll help.
You've got this, don't give up!!! 😁
-jinx_58