I recommend that students studying for a PT cert, study until they feel comfortable with the material. Most certification programs can provide the materials to be covered on the exam for a fee. Or you can find the materials through other sources, just make sure you have the latest editions, etc.
I have taught a many students in the past at a nationally accredited post secondary program and I still teach students now in my own program. I find that it is helpful to get some practical experience as well and to network with workng personal trainers. There are sample tests available as well.
If you feel that you are weak in any area (you mentioned anatomy and physiology), definitely put in some extra effort there. And one last bit of advice, I know several trainers who failed their first attempt at certifying. Most of them found that taking the exam gave them insights into studying for the retake exam. And I don’t remember any of them failing it twice. I know that a few of these people are very good trainers now. Life is about take a chance and learning from mistakes. Don’t over think it or worry. Good luck!
If you want to discuss this more or any fitness topic, contact me through my profile. I am in the process of getting a new website up.