How do you prove anxiety to a doctor?

New in here, been experiencing debilitating anxiety in specific situations since I was 12 years old (currently 22), this anxiety prevents me from performing on certain academic settings. Not in the way of preventing me from preparing and working but by being unable to write or talk from the shaking, dizziness, heat, etc.

After going through horrible experiences I finally decided to look for professional help, I want to see my doctor and explain him the situation in hopes of him giving me meds to only take in those specific situations (not everyday).

How did you guys do it? I'm afraid he will downplay the situation since I know of doctors that just tell you that you need to overcome the nervousness. I do 100% have anxiety since I experience almost all symptoms.

Thank you.