Preparing for a test that plays a large part in determining your future path will ALWAYS be overwhelming. Sure, studying got easier for me, but it was continuously overwhelming because I knew that my success on this test mattered so much. You learn to deal with it and compartmentalize that feeling, though, so that you can learn more efficiently. Don't worry! Things will be fine. I also constantly worried that I didn't retain anything and was still doubting myself even up until test day. It got to the point, though, where I just couldn't stand studying anymore. I figured that meant I needed to just suck it up and go for it. And guess what? I realized I had retained stuff! 🙂
Best of luck! 😀