You probably should NOT be concerned, but you need to dig into your results a lot more deeply to know for sure.
First, as a general rule, progress on this test is not linear. Most people do not see a significant score difference for the first 6 to 10 weeks. You've learned a lot of stuff, yes, but you're still probably slow with a lot of that stuff, and slowness affects your overall performance. Plus, there's a lot of stuff you haven't even earned yet.
Second, though, as I mentioned, you need to dig into the results more deeply to tell whether you're making good progress. You care about the things that you have already studied, and you care most about the things you started studying at least several weeks before the test. (It's not reasonable to expect a big improvement in an area you just started studying 6 days before the test.)
Use this article to help you analyze your results:
http://www.beatthegmat.com/a/2009/09/23/evaluating-your-practice-testsFigure out your major strengths and weaknesses using that article to help. Notice the things that have gotten better since you started - you're on the right track there. Notice the things that you've actually studied that have not gotten better, and start to figure out WHY. Notice the weak areas that you have NOT studied yet, and make a note that when you get to those topics, you might need some extra time (and you can gain that extra time by noticing your strengths in areas you haven't studied yet!).
If you have any questions about your results or just want to talk through what you find after you do the analysis described in the article, let us know!