It's hard to say without knowing much detail, but here are a couple thoughts.
How is your timing? Do you consistently run out of time or finish too early? If so, your score can be greatly affected and if you fix the situation you may be able to bump up your score without needing to suddenly learn anything new. One way to manage timing is to write on your scratch paper two columns representing the question number and your target time. Something like this:
Q T
4 28
8 21
12 14
16 7
20 0

Basically, every 4 questions you can look at the clock on the screen and see how it compares to the target time in the right-hand column. If you see that you're falling behind, the solution is not to speed up! You'll just start making sloppy mistakes. Rather, the solution is to skip a problem that looks tough. No reason to waste time on tough ones when you could have easier ones up ahead. The columns I depicted are for Quant. Verbal would be the same except that you should count down by 6s in the clock column since verbal should be 1:30/question.

Secondly, it sounds like you don't have an error log. In a 4.5 month long process, how did you determine what topics to study? That's a lot of time invested but if you were studying things that weren't as important for you than you may not have been as efficient as possible. Long story short, you need to go back to the tests that you've taken, and put all the questions you got wrong into a spreadsheet. You should also put the ones you got right in there if you spent more than about 2:30 on them. The spreadsheet should also tell what topic (i.e. algebra, word problem, overlapping sets, or main idea, inference, detail, etc) and what question type (i.e. quantitative comparison, multiple choice or reading, sentence completion etc.) Then you can study the trends and see where you're losing the most points. Those are the areas you should be studying. If you lost a total of 5 points from probability, but 12 from word problems, then obviously studying word problems is your priority. Once you've studied it some more and worked out your issues, then I'd go back and redo those 12 problems I'd missed in the past.

Hope this helps.