Are you in high school? Just want to make sure.
One thing that will help you, if you are still in high school, is to be more flexible in your thinking about the future. Planning too far in advance can cause stress and also actually limit opportunities, because you are more rigid with such concrete goals.
Sorry for the side comment but your panic at this grade seems related to a future goal that is far away.
Many people who are talented in math experience this kind of thing. As you said, it is a problem with test-taking. You will improve. If you love math, don’t let this set you back or make you despair.
If you are doing math because of your stated future goal, though, try to stay flexible about plans and follow your true interests and talents as you make your way through college.