Moving to another area and getting situated there can be very stressful. He may have not yet felt quite grounded there (he may be questioning if he himself wants to stay there)
Another possibility is that he may feel that once you move there things can get more serious and that he is not ready for a large commitment. Dating someone for 5 months does not always allow for the people to get to know each other as well as if they had been together longer. There can be many speculations as to why he had said something and the only way to know for certain is to ask him maybe over the phone versus email. At least you could make things clear on your end that you feel committed and as you've mentioned had even applied for jobs there.