My first long term girlfriend was just the opposite. I often wondered if there was something I could give her to make her not talk so much.

Don't feel that you have to talk all the time just because you think others believe that you should talk more. As the Talking Heads song goes, "When I ain't got nothing to say, my lips are sealed. Say something once, why say it again?".

I think a lot of if comes down to confidence, and the ability to say whatever you want to say without worrying if others will think it interesting or in some way worthy. When you get to this stage, then of course, some people will like what you have to say, some will love it and others you will bore out of the room within a few minutes. But who cares?

I don't think that quiet people have fewer thought processes going on inside their heads. They have their own multitude of opinions on any and every subject and have things they are interested in and are capable of talking about. Achieve confidence in yourself and the talk will flow.