Here's a suggestion: Go to your campus disability services office and have them help you. They work with anxiety disorders, all types of disorders actually, which translates into getting more testing time and being in a private room to do so as well as many other helpful tools.

Working while going to school is very difficult. You've already recognized that your ability to concentrate works better with less classes, so that's a good start in meeting your unmet need. Let's hear it for the brain in letting you know that! Also, online classes might be more calming to your brain circuitry, too. Please explore your options before declaring yourself noncollege material.