Given your PR scores, I would recommend you to practice questions on this board and try out Kaplan. PR scores are usually pretty representative of the score you may get on the actual exam. Since you already used the OG, your PP score may be skewed upward. While Kaplan will help you boost your math comprehension and solving speed, problems on this board will help you fine-tune your skills.
I cannot but emphasize the word "practice". Keep practicing. However, you have to do so in a methodical manner. You have to understand where you made your errors and go back to those problems after a few weeks to see if you mastered the concept. If you are not sure about certain concepts, post them on this board and see what people think or how people will solve it. Ask question! Do not be afraid of asking questions however stupid you may think they are as it will help other people and yourself better understand the same problems. Sometimes, it is certain basic concepts that are forgotten as GMAT math is base on college math which is for most of us, light years away. For instance, people tend to forget that 0 is neither a positive nor negative integer but it is an even number. Also, there are certain math "tricks" which will help you better solve slightly tougher math problems. For example, can you find the units digit of 3457^358?
All I can say is visit this board and you will find much useful advices given. Just participate and you will see the benefit of doing so. Good luck