Most Helpful Guy
If he can't tell you a reason, it probably is taht he just feels he is too young to be tied down in any relationship long term..with anyone.
It's not a question of anything you did or didn't do. He has decided a relationshp doesn't work in his life right now.
He sounds like he will stay a good friend, which means a lot. Most people don't have a good friend.
So think of the cup as half full! At least you have a reliable friend.
Stay in touch with him, and don't press him about the reasons he pulled back. He probably doesn't know himself! Just be a friend right back to him, and see what the future might bring.
Will you get back together? No one can say for sure..but pressing him will push him away, that much I can tell you.