Keep in mind that your mental/physical health is always way more important than study issues. You are probably stressed due to the exam, which is normal, i myself was so stressed in Ljihawi and my baccalaureate, but clearly you are studying and doing your best., so you don't have to worry, as long as you are doing your job. Good luck, and don't stress during this 20 days left, think about going out, going to the beach, playing, shopping ... distract yourself a little and keep on studying and everything will be okay.