I had the same problem, I'm guessing its because you are probably spending too much time referring back to the passage to check your answers. Contrary to common sense, you shouldn't be referencing back to the passage to check each single answer or even 80% of the answers. In fact, I might look back at the passage for 5 out of 40 questions at most, but I only do this because I know exactly where to find the information I'm looking for and to differentiate between two answers that sound good. Verbal is more about getting the author's main idea and using that to eliminate answers that the passage never mentioned or aren't part of the author's main idea. Once you start taking so many VR's you'll begin to realize that on 90% of the questions, usually 2 are obviously wrong, giving you 50:50 odds. Try going with your gut answers on the next VR you take without referring back to the passage too many times and see if this works for you. I wouldn't expect immediate results over the first test by doing this, but after several practice tests and making sure to learn why the correct answers are right you should improve dramatically.
I don't claim to be a VR expert, but I've been getting consistent 10's-11's on the AAMCs and once you start scoring 11's the difference between 12/13/14 is only a few questions.
