Hi Gabriel,
A score can dip from one exam to another even with the same amount of knowledge or the same percentage of correct/incorrect. The GMAT scoring algorithm takes many factors into account including where you make errors, how many mistakes you commit in a row, whether you finish both sections or leave questions out, whether the last few questions of either section seemed like they were guessed at, how you felt on test day, etc. These factors can all affect your score. From one test to the next you can easily jump +/- 30 points (and even up to 80 or so) depending on where the mistakes are. *Where* you make mistakes can often be more important than how many. Overall, when a student wants to know where he/she stands, the best way to do so is to take the average after a few sim tests.
With that being said, I completely agree with the above post. For the meantime do not focus much on practice tests, rather focus on your areas of weakness. It might be best for you to get setup with a good adaptive course that will determine these for you. If you need a recommendation, just let me know. Once you have determined your areas of weakness and mastered them, I would then go back to overall coursework and sim tests. For Verbal specifically, go back to the beginning and work on grammar basics. Usually when a student is having such issues, it is because they are missing a few of the key concepts to the basics of grammar. If necessary grab yourself a good supplemental grammar book to use in addition to your current studies. I can also provide a good recommendation for that if you are interested. Did you already book a date for the GMAT? If so, it might be best to extend your study time until October. No point in taking it just to have to retake it. So if you don't feel ready and you can realistically extend your study time without it affecting your life's plans, then definitely go for it. If you have any other questions in the meantime, please feel free to ask me.
Good luck with your studies!
-Evan