It is not clear what your verbal problems are. If it is simply that the English is difficult for you, you may need to spend time on vocabulary and grammar so that you better understand the questions. If you haven't worked with a tutor, a few hours one-on-one with an experienced GMAT tutor may help you to identify specific issues to work on. That can be more productive than simply going through a prep book again. If you are not a native speaker, schools will look closely at your AWA as well. If that is also low, they may be rightly concerned that you will not be able to follow the class discussion.

When you say you cannot concentrate, that implies that you are very stressed on that portion of the test. Kaplan offers a stress workshop that may help with test anxiety. Being able to relax and focus is critical to obtaining your best score. I hope some of these ideas will help you bring your verbal score up to a level more in line with your excellent math score.