Sounds like you have no idea what you were trying to improve the second time. If you're blindly studying and just putting in the hours, you're doing it wrong. Second, if you think that "I'm a horrible test taker" is an excuse to get by in flight school on tests, then you're already wrong.
Look at it this way: the world is a series of tests. Some people are intelligent in such a way that they never have to figure out what to study, because they already do it without trying. Others have to learn what the tests are testing in order to study right and do well on the tests. Still, others never learn what the tests are testing and study to no avail, ultimately not learning what they really needed to know to get to the next level.
You sound like you're in the 3rd group. Learn how to put yourself in the 2nd group. What is the test really testing? What do you have to know, just for this test? If you can do that, you will be more successful and at least have a shot in flight school. Not saying the ASTB is the end-all-be-all for flight school performance, but the chances are good that you'll have difficulty performing well in an environment that is all about test scores and studying. At this point, you can do no harm to apply and see what happens, but I highly suggest learning how to put yourself in the 2nd group.
And, good luck!