Please start revising NOW! it is never too early to start preparing notes.
If you make notes now, then you will not be stressing during the exam period, and all you will have to do is read over your notes and do past papers.
In the next few weeks, your teachers SHOULD be giving you past papers, revision sheets etc. DO THEM! it will help enormously.
Don't do all nighters - they DO NOT WORK! work to 12 at the latest, and get a good nights sleep. This is the best thing you can do. You won't remember ANYTHING if you do an all nighter and you do not sleep.