Your concern is one that many students express. The good news is that there definitely a way to improve. First off, I would recommend making mini-summaries after each paragraph. These don't have to be more than a few words that capture the gist of the passage. The key is not to look at the paragraph after you've done reading it. Rather force yourself to come up with a mini-summary based only on your memory. At first this may be difficult, but by forcing yourself to look for meaning in the paragraph, will lead you to actively engage the passage.
Repeat this strategy with each paragraph. By the end of the passage you should not only understand each paragraph but should also have a sense of the main idea of the passage. Once you become adept at writing down mini-summaries, start doing mental summaries. That is, force yourself to make a quick mental summary after reading each paragraph.
At first do not worry so much about time. Indeed, time can nip this strategy in the bud, and force you to rush through the passage. So take your time implementing this strategy. In the long run, paraphrasing in your head will save you a lot of time once you get to the questions (you will have a better sense of where to look for key information and will be able to answer questions with more confidence).
Finally, remember that very few people find the passage interesting - the key is making the passage interesting by engaging yourself the way described above.
Good luck, and let me know if you have any questions
Magoosh Test Prep