You're exactly like me! I was a very playful kid and I spent all my time outside, I got in a lot of fights and brought problems back home to my parents, I was very popular and friendly but things changed over the years. Now I am always indoors and hardly mingle with people, I always come up with an excuse whenever a friend invites me out, I just want to be on my own. You're not alone bro, a lot of us also have the same experience and it's not weird