Here is my theory for what happened. Let's imagine there are only 10 questions, and a score of "1" is an easy question, and a "10" is a hard question.
Let's say you get questions 1-5 wrong, and questions 6-10 right. Then the difficulty of the questions you face (and therefore the potential points) might be as follows:
5, 4, 3, 2, 1, 1, 2, 3, 4, 5
Let's say you get questions 1-5 right, and then questions 6-10 wrong. Then the questions you will face might be:
5, 6, 7, 8, 9, 10, 9, 9, 8, 8
It seems to be the case that answering easier questions incorrectly will hurt you more than answering hard questions incorrectly. You simply cannot recover.
Based on your other test, clearly you have the ability to do well. Just analyze what you did wrong in this test and apply your learnings to the next one!