but I figured I'd score at least higher than my original score
Actually - and surprisingly - not really. A lot of people either stay the same or go down on their 2nd practice test. It's a nice surprise if you go up - but that is more of a surprise than staying the same (and a 30-point difference is really staying about the same).
Why? Well, you've learned a bunch of stuff in the last few weeks, but you're still practicing it. You're still making mistakes with it and - this is the big point - you're slower than you will need to be by the time you take the real test. That slowness messes up everything else when you're taking a practice test because the time is so very limited. You're trying to remember: "oh, yeah, what kind of problem is this again? Right, and then I'm supposed to do this, or was it that? No, this. Okay, got it." And the extra 20-30 seconds you're taking every time this happens means you've got to take 20-30 seconds from some other problems - so you either move faster than you should throughout, causing lots of careless mistakes, or you run out of time at the end, causing a string of wrong answers - either way, your score is affected.
So, that's what's happening as far as your overall score goes. Now, here's the thing: you
have improved in some areas, but the overall score is not going to show it at this point. Go take a look at the specific test results. Run the assessment reports and see: where am I doing well? Where am I not doing so well? Pay particular attention to the areas you've actually studied over the past few weeks. Also, compare your results to the results from your first test. What are the steady areas (in terms of what stayed about the same, performance-wise). What areas improved? What areas declined? WHY did they decline? You might discover, for example, that you suddenly did much more poorly on fraction problems. And then you look at the timing and realize you were going kind of fast, hmmm, and then you look at the problems themselves and smack yourself for making some careless mistake... and, oh, it's not that I didn't get better. I did get better at what I'd studied*. But then the timing thing affected my performance in other areas. Okay.
*Although, of course, you won't have gotten better at everything you studied. That's part of the trick - what worked? Check those things off your list. What didn't? Add those things to your review list for the next few weeks.
So start with those test results. For the areas that you have NOT studied yet, figure out what your weaknesses are (not just percentages correct - timing also!) so that you can appropriately prioiritize when the class gets to that point. For the areas that you HAVE studied so far, figure out what is working totally (accuracy + timing is good), what is working partially (accuracy OR timing is good, not both), and what isn't working (accuracy and timing are both not good), and start reviewing accordingly.
Also, get out the Review Your Work handout from class 2 (or you can download another copy from the Class Resources / course downloads section of your student center). As you review problems from this test, from homework, etc, this handout is your "bible" - it tells you what questions to ask yourself and how to review.
When you finish studying a problem, you need to be able to say to yourself: okay, if I see a different-but-similar problem in the future, I'm confident that, first, I will recognize that the problem is similar to this one and, second, I'm confident that I can do what needs to be done within the expected timeframe to answer the question. (Notice that I do not say "I can do what needs to be done to answer the question
correctly." First, we're all going to get lots of questions wrong no matter how much we study. Second, taking 5 minutes to get something right will actually end up lowering my score, because I'm going to get at least 2 other questions wrong as a result. There's always a trade-off. So, sometimes, my best outcome is to make the best possible educated guess within the expected timeframe - even if I get it wrong.)
I also strongly encourage you to talk to your instructor. It sounds like you've been in class for a few weeks now, so s/he should have some idea of your strengths and weaknesses (assuming you participate while sitting in class - you do, right? If not, start participating!). So ask your teacher for more advice, too! :)