The key to improving your score is to learn from your mistakes. For each wrong question, try to find out EXACTLY why you made the mistake. Invest your time to ensure that you won't make the same mistake again. Repeating this process will improve your score because similar questions will frequently appear.
Understand that doing well on exams isn't the ultimate life goal. Don't be too overwhelmed because it's just one of many challenges that you will gracefully conquer :) Approaching exams with this mindset not only makes the process more enjoyable but also often leads to better results!