is it possible that you have some fears around officially "dating" or moving in together? Your own fears might be triggering his fears, even if they're subtle.
As far as moving in together, have you tried doing weekly sleepover's? Would the two of you both leave the places where you are and move into a completely new place? Does he have any of his stuff at your place or you have any stuff at his? More than just an overnight?
If he has personal stuff at your place, it will feel more comfortable for him. If you have stuff at his place, he may feel more comfortable with the idea of you being a constant part of his life.
