Why is he ignoring me?

This guy and I were friends in middle school, but I moved away the summer before freshman year started. He always flirted with me, but I wasn’t interested in him then, and basically started ignoring him. This summer (3 years later) I saw him out and I started talking to him over facebook. He gave me his # and told me to text him. I did, and we texted for 2 weeks nonstop. We even hung out together once. The only thing is he seems really insecure and even got mad because he thought I liked his friends. We had a good conversation one night, and the next he wouldn’t even talk at all. What’s going on? I’m not sure if it’s his insecurity or what :(