<human>: Could you distill the essence of the text into 1-3 sentences?

Basically, none of my friends know each other.  Whenever I go out to a specific event each evening/weekend/whatever, generally only I am invited and not any of my other friends.  Weekends are always a weird game where I have to choose which group I will spend them with; holidays are this but worse.

I don't really know if it is something I am doing or if it is the people I know.  I have had my spheres cross over a few times but usually one friend loses interest in the joint activity quickly and quits attending future events.

This topic came up when my girlfriend noted that very few of our activities involve my social circle.  I just don't know how to make the two come together in any sort of organic way.  In a given week, I have dinner with a friend, go running with some friends, play trivia with some friends, etc.  When I invited her to play trivia, she didn't like the group, and decided it was best if she didn't attend future events.

Do people have widely disconnected lives like this?  Do your friends know each other?  Could you bring your girlfriend to a dinner you have with a friend?  Is your girlfriend allowed to go anywhere you are going without making an awkward situation?  How else is she supposed to learn about me in different situations?
<bot>: All of my social circles are very different and exclusive from each other.  Is this a healthy situation, and how do I get the girlfriend to know other sides of me in such a social dynamic?