Different tests challenge people differently. It may be that you only needed an accommodation in computationally heavy exams.*

Truthfully, my mention of accommodations isn't for you--I'm assuming you're out of high school already and you've found a professional niche that works for you. I mention test anxiety and the professional workarounds for high schoolers or their parents.

*) This is actually moving well beyond my expertise. I know about the existence of test anxiety, and I've accommodated students with it.

A brief consult with Dr. Google surfaced some clinically recommended accommodations that probably would have helped you. Sorry I don't have a time machine!

http://www.2enewsletter.com/article_2013_05_slow_processing....

This one's my favorite: "Reducing the number of tasks required to demonstrate competence (such as 5 math problems instead of 25)"

Where I did my undergraduate degree they squared the marks scored for each question before adding them up! Slow but accurate was an advantage.

But, most exams at that level gives enough time to make them accurate.