"This is your anxiety....it's not a brain tumor." You need to tell this to yourself over and over and over and breathe deeply.
You don't have a brain tumor. Anxiety makes me feel dizzy, lightheaded, off balance. I had twitching all over my body, numbness, you name it. I had workups for it as well, a head CT scan and an EMG. I have been down this path with brain tumor fears, so let me reassure you...
I went to the neurologist CONVINCED I had a brain tumor and I will tell you what he told me verbatim. "I can tell if someone has a brain issue watching them walk down the hallway to the exam room." There are SIGNS that people on the outside can SEE, not just physical symptoms you experience.
My friend had a brain tumor and her first SIGN was she stopped being able to speak over the course of a week. ONE WEEK. SHe didn't have symptoms other than some confusion before that happened.
BREATHE. And listen to the doctor.