Hi 16095148D.
I have a theory for you.
Here's the thing.
When you take a math test in school, the questions that you see on the test look at lot like the questions you saw in the homework. So, if you totally understand how to get all of the homework questions correct, likely you will get a high score on the test.
The GMAT is different. Even the quant part is a test of reasoning skills. So, when you take GMAT quant, you aren't really taking a math test. You are taking a test that involves math but also tests reasoning skills, and knowing how to answer the
OG questions is not at all guaranteed to get you a high score on GMAT quant, because, unlike the questions on a normal math test, the tests on the GMAT often won't look that much like questions that you have seen in the homework, i.e., in the
OG.
So, here's my theory. When you took a practice test before preparing, you didn't know what to expect. So, you used your math skills and your reasoning skills, and scored Q44. THEN, you prepared for GMAT quant as if it were a math test, by working on
OG questions. Having done so, you got into your mind that what you would see on the test would be like what you had seen in practice, but what you saw on the test was not like what you saw in practice. It had different tricks and twists, and you both didn't know how to handle them and had preconceived notions of what you would see having focused on the
OG questions for so long. So, maybe you developed the appropriate math skills a bit, but you didn't use your reasoning skills as well as you had used them on your first practice tests, and your scores on the last two tests reflect that change.
So, what's the answer? Part of the answer is for you to do what others here have suggested and build a broader and deeper skillset by learning GMAT quant from the ground up. Also, you have to go beyond using
OG questions for practice and use a much greater variety of questions, so that you go beyond learning GMAT math to learning how to apply that math in a large variety of situations. Finally, I believe that another part of the answer is that you have to remember that GMAT quant is not just a math test but also a test of reasoning and execution skills and prepare accordingly.