Hey,
It's normal to be anxious however you don't have to fear.
A good pdoc will listen and ask questions to determine if you need medication.
It's just like going to see your regular doctor except for your mental health.
It's very good that your mother is supportive. If you like, perhaps she can wait outside while the pdoc talks to you. The doctor might also want to talk with her to get more information on how to help you.
You'll be ok and you'll find it's not as scary as it seems to be.
Social anxiety can make it hard to talk to the doctor, but remember that he's there to help you. You can write down your symptoms to give it to him as well, if you're afraid you may become too anxious to speak.
Good luck!