The fact that you're seeking professional help to manage and help with your anxiety is excellent and the first step in the right direction. You'll want to go beyond seeking and legitimately speak with someone if you deem it necessary (maybe you already have but your post wasn't too clear on that.) The only advice I can give that has worked for me is to try and change your relationship with angst itself. Acknowledge the discomfort and really stew in it. Don't think of things that would increase your anxiety. But just feel it. Then analyze it. Why are you feeling this way? Why is this happening? Is this logical? You went on a date with this girl... Clearly she must have some interest in you. Focus on the positives you bring to the table. Convince yourself that your angst and nervousness In this case are a good sign. It means you perceive value in this potential relationship. It means you like her. Just be as good to her as you can... And don't beat yourself up if things don't work out. Just learn from the relationship and be a good dude. Enjoy yourself.

Good luck.