Friends come and go, and there's not much a person like you can do about it(quiet, introverted). As time goes on a select few people will decide that they're gonna stick to you and take you into their friend groups. Before you know what happened, you'll go from worrying all the time about how to talk to people, to having more friends than you can keep up with. These friends will come in and out of your life for reasons typically out of your control, so instead of thinking about others all the time, focus on you and your relationship with yourself, because you'll soon find that it's the relationship that matters the most to you.