A lot of the problem is that you're mixing apples and oranges. By that I mean that introvert and extroverts are virtually the opposite of each other. Introverts are energized by being alone, and crowds wear them out emotionally and physically. Extroverts can't stand being alone as it wears them out emotionally and physically but are energized in a crowd, and the outgoing a person is, the bigger the crowd they love being in.

Here's a quote that helps me cope with being an introvert as I think it summarizes us to a Tee: introverts aren't party poopers, we're pooped by the party.

Look for friends who are more like yourself. You can be casual acquantances with the social butterflies, but realize you're too different from them to ever be close friends. Don't try to be or you'll be very frustrated as you won't understand them, and they'll never understand you which will make your anxiety much, much worse.