I found myself having this same issue a few weeks ago. What I've realized has helped me is taking a 5-10 second break after every paragraph in the passage and actively reflecting on the paragraph I just read. This helps me better understand not only the paragraph itself but how the paragraph plays into the grand scheme of the passage. If your issue is answering all of the questions too quickly and then getting them wrong this might be a helpful tool to slow down and attack the questions with more accuracy.

P.S. sometimes reading passages in a voice different than my own helps me to read more actively.