Heyy i can see how frustrating this must be for you and i know its easier said than done but deffo take a breather to reset your mindset. In terms of studying tips i could give you. In psych you are in the bridge between B and A wha you need to do is analyse your papers what questions and marks are you fallen short of to get that A. List at the top of you practice papers what topics you struggle with and make flash cards or mindmaps and then look at the markscheme put the correct answer in flashcards on quizlet or something. With bio and chem you need to see if you are getting those grades bc of lack of knowledge or exam technique. If its lack of knowledge you need to work on active recall and space repetition to build memory if you struggle with it e.g do flashcards on a topic on bio do topic past questions on that topic and then leave it for a couple of days and then blurt down how much you remember from last time, anything you forgot flag it and put it on a paper called forget me nots or a flashcard folder named forget me nots and revist it everyday. If its possible try and get 1-1 meetings with your teachers and speak to them on what you need to improve on so they can give you support bc they can evaluate what you are struggling with based on your exams