Don't panic. Panic is useless. You may not pass the exam with perfect marks, but there's still time to rescue your year. Here's how.
1) Think like an examiner. I say: What's on the exam? "Everything," you say. No. Wrong answer. Not possible. Remember that, in an exam, you have a limited amount of time to show that you can work with the language you learned in class, and an exam is probably going to focus on the skills and language that you need for your level.
If you're a B1 student (EOI Level 3), for example, your teacher needs to see that you can express opinions correctly, ask other people about their opinions, and compare and contrast things and people. Your exam, therefore, will probably check that you understand and can use comparatives and superlatives; that you understand how to express opinions properly (I think that, If you ask me...)
2) Don't believe the "PERFECT" myth: "PERFECT" does NOT exist. Know what "perfect" is? It's a trick that people use so that they can have an excuse later on for not trying - because they KNOW that speaking English perfectly is impossible. Don't try to be perfect. Just do your best.
It's the same with sports. An athlete who puts pressure on himself to be perfect gives himself or herself too much stress, and is destined to fail; athletes who compete doing the best job they can almost always do better than the ones who obsess too much and end up failing because of stress.Use the English that you know and understand to do the task on the test. That's all you need to do.
3) Choose your battles intelligently. Don't waste time studying things that don't give you problems.
Before you start studying, take a piece of paper and divide it into three columns. At the top of the first column, write "NO PROBLEM". The second column is called "MAYBE." The third column is the most important: "NEED HELP".
Now, go through your notes and put each topic - vocabulary, grammar, pronunciation - in the correct column. If you can easily talk and write about the topic, it goes in "NO PROBLEM" and will not require a lot of review. On the other hand, if you have trouble remembering the relevant vocabulary and don't think that you could easily talk about the topic or use the language that is connected with it, it must go under "NO PROBLEM".
Why should you do this? If you only have a week or two to prepare for your exam, it's important to distribute your time in the most efficient way possible. You cannot gamble and hope that the exam will only include the topics you know best. Identifying the worst problems allows you to review in a productive way. Even if you don't know the topic enough, you still have a chance if you guess (and on the Cambridge Exams, points are NOT deducted for an incorrect answer.)
4) Ask for help. Ask me. Ask your teacher. Ask other students (remember, none of you is as smart as all of you are together.) Ask an English speaker who you know. Check English-learner websites on the Internet; look in the back of your textbook and see if your textbook publisher has a companion website for your textbook (where you can get extra activities and advice.) The squeaky wheel gets the grease: You only get as much help as you ask for.
Good luck!! And stop procrastinating!!