If you've only got two weeks til exams, try working through problems from Physics and Maths Tutors. Even if you don't solve all of them, reading through the question papers and mark schemes side-by-side will help you remember the information and how to answer the questions. If paper revision e.g. flashcards isn't working for you, watch revision videos. Also, go through your coursebook and just refresh your mind on the content. Seneca is also really helpful as a revision resource because it combines revision notes/explanations with questions. Positivity will help you focus, so focus on what you can do! You can learn a lot in two weeks. (I do physics not chemistry or maths so I can't say anything in particular about your subjects, sorry.)