As a kid, I was also painfully shy. I found that it made me a good listening post for people, and extroverts would seek me out as a friend b/c I listened a lot more than I talked (mostly out of awkwardness or not knowing what to say).

Over the years I've found myself being a better and better active listener mostly because I hate when people don't actively listen to me. Think of those awkward times you've started a story in a group of friends and realize nobody is listening - I am always the person making sure someone is listening.

So I guess my point is that you're just exhibiting good active listening skills, which you've learned over time. Honestly, I wish more people would learn them, because it really can make you more likeable and easier to talk to.