This is a very difficult time for you, failing even once is rough. You feel like you should be a nurse by now and that you're waisting your time and energy.
I know how that feels. I failed 2x.
What advice I can give you other than what my friends said, is to use that frustration, sadness, even anger to fuel your next attempt. I found that using my emotions to "kick my butt" reminded me how important this was to me! I worked hard every single day, studied content until it ran out of my ears and did question after question. I know you feel you did the same thing, I'm only suggesting you do it again, get up and try once more. Give it everything you've got and don't look back to say you could have done more. That will help your confidence when you take it.
Secondly, there is most probably nothing wrong with your knowledge base. You have learned more in this study period than someone who passed their first try, so I would say don't start with knowledge study. Look at your weaknesses. The board sends a diagnostic profile of where you fell short. Use this to your advantage. Make a list of everything you feel even remotely unsure of and be sure to cover that before taking the test again.
Then, I would suggest looking into a private tutor or a review that teaches you how to look at the question and pick it apart, use knowledge to answer, and apply test taking strategies. Ofcourse there is Kaplan as a universal answer to any state, but I would suggest a private tutor to boost your self-esteem and confidence. Having one on one help is awesome. I know that is how I passed my third try.
Overall, hang in there! You can and WILL pass this test, you just have to keep plugging away and find out what is your biggest obstacle. Understanding why you are failing is the first key to passing.