I agree with PPs advice about getting in a rut and how the sparks aren't there all the time when you live together.
First, I appreciate that he is being honest with you before making you commit to a move. He's at a point where he's either going to grow out of that puppy stage of love and recognize what real commitment and love can mean - or he's not. Maybe he isn't ready for that step yet, and that is okay. We all mature at different rates. I suggest not making any future commitments until he sorts that out, though.
Second, I was actually in a similar emotional situation as your bf, I think.
Before my now-husband and I started dating, I was in a 2yr-headed-towards-the-alter relationship with a man who joined the AF after 1.5 years dating. The first little while the spark was there 100% because we were a new dating couple. The second part of the relationship the spark was there because of LDR. We never lived together. The relationship was very passionate and exciting, I treasured every moment we had together - but he went crazy and left me and tried to get me back and I said no...that's another story, though. Let's just say it was extremely hard on me, very painful.
The dating relationship with my now-husband was MUCH different. It started LDR and ended up with him moving to my state and living with me. The first few months were new and exciting. 100% sparky :) However, he is a very different person from ex-bf. He is calm, steady, quiet - not very demonstrative. But he loves me, in his ways :) The crazy 100% sparky died off after the newness wore off. Things became habit. When he proposed, I said yes - I knew logically he was wonderful and I wanted to be with him. But I did have a bit of an emotional crisis. It took me some time to realize that the spark is not what makes a strong foundation for a marriage/long-term relationship. I love my husband with all my heart, and I'm so so happy I made the right choice to marry him. For me, I was just looking through rose-tinted glasses at the past, and I'm sure some of it was due to cold feet.
That spark is puppy love - It's fun and exciting and I'd be lying if I said sometimes I didn't miss it. But I miss it like I miss college or HS - like I imagine parents miss when their children were babies. I don't actually want it back - I much prefer all that comes with my quiet, steady man :)
There is also the potential that he's not ready for marriage or other long-term commitments and he doesn't want to screw you over. Hard to tell from the post, and it sounds like he isn't sure yet either. But at least he's trying to be honest with you - I'm sure it's driving you crazy - I'm sorry you're in this situation. ((hugs))