Most Helpful Guy
He's 100% insecure. Maybe someone said something to him or something happened in his life, regardless it's evident he's not the same anymore. Just talk to him, be upfront. If you don't reach out to him it is just as much your fault as it is his that things didn't work out between you two. In any form of relationship you need to be able to talk about things like this :)
Most Helpful Girl
Maybe he was afraid of the way he feels for you.
And why don't you write him?