Need help understanding what happened here...

So, I have Social Anxiety. I'm a big guy, both in height and width. My therapist at one point told me that I come off like Eor from Winnie the Poo (I liken it to Rays brother from Everybody Loves Raymond).

To the point. I'm getting out more often on my own, and was at a store buying some alcohol today. The older lady behind the counter seemed cool and sweet. I'm 30 years old and look young, so she asked for my ID.

This is the exchange.

Lady "Oh, you have a birthday coming up soon."

Me "Yeah, soon soon. Thinking that it's too soon. It's funny how when you get older you don't want them to come sooner (silly joke). Know what I mean?"

she looks at me, and throws her hand up.

Lady "Stop talking to me."

Me laughs

She finishes the transaction. I smile and tell her to have a good one. She doesn't even look at me, says bye to other person leaving.

I then realized as I was leaving, she was being serious. And, now I'm running through my head all the things that could've went wrong.

Thoughts?