M.M.
I have moved across country with 3 kids, 15 months apart, all under 4...temporary housing while goods were being shipped, etc. It WILL get better, it IS traumatic for everyone and some regression is to be expected during stress.
Try to pretend it is a vacation and go out to explore each day and make a "happy list" to recite with him as a bedtime ritual (or any time he's worrying). In strange situations a child may get so emotionally exhausted they sleep too hard or are afraid to get up in the night.
All will be well again when he trusts that you are in control and happy about the situation. (Tough to "pull off" I know, but important to him to know grown ups are handling the scary stuff and he can just enjoy lots of eating out and other things that moves bring.)
P.S. The next time I moved across country with the kids they were 7, 8 & 9...it does get better but never without a glitch or two. Hang in there and when it comes to smiling "Just fake it 'till you make it"!) Good luck!