My advice would be to start UWorld now. If your exam is in November, you need to start reviewing the content as soon as possible. Don't worry about getting questions wrong for which you haven't reviewed the material yet. You can learn it when you read the answer explanations. You can certainly achieve a 200 now if you've been reading First Aid actively, like the above poster mentioned. If you take an NBME and your score isn't where you want it to be, don't be discouraged. You really start to rise as you go through UWorld.