Are you reading the answers first?

Don't read the question. Treat it like Jeopardy, read the answers and think of the question they would be correct answering.

Just be reading the answers you will generally immediately be able to rule out at least on if not two just based of the grouping. Two answers will generally be the same or related and two will be a little off. Now you know what the question is asking, because you know the only possible answers.

Then you read the question and it has some context making it easier to answer.

Additionally stop and ask yourself "what are they asking". Many people fail these (and other test) because they over think. They start thinking and imagining the questions and scenarios in real life, or what they would actually do or have seen. Bad call. If you read the answers and you then read the question and still don't know. Stop and remember that the question was written with the intent to hit on some core principle. It was likely in the book in one of those boxes off to the side, or a specific vocabulary word in the chapters. Don't get caught up in their scenarios and distracting information.

The NREMT loves to give you three sentences about a complicated scenario and then ask you a simple question about normal respiration or something totally unrelated to the specifics of the case the presented. But you're all wound up because the just talked about some sever respiratory peds PT and then just asked the normal respiratory rate for an 8 year old. Could have asked just that, but they want to test you reading comprehension as well.

Finally, the most common mistake is missing words like "except", "not", etc. Reading the answers will help with this as those grouping necessarily have a pattern, three things must match and one won't. So that will help, but I also go out of my way to write down NOT on my scratch paper when I get those questions, just to remind myself.

It sounds like you need a book on test taking or study skills as you are putting in the time... don't get discouraged, some of the best EMT's and Medics I know failed NR for both, some more than once. It's a silly test.