A.F.
Hi A. :-)
It sounds as if your little one is fearful of his changing world. Just when he was getting a grasp about his world and how he fit into it.. he "wakes up" one day and it is completely changed.. because daddy doesn't live there anymore.
I agree with Sommer G in asking how long ago this divorce occurred? His living arrangements are probably different since I heard you mention your mom so he may need some private time with you and then dad and then TOGETHER.. to explain how daddy still loves him but now he lives somewhere else and so do we! Something along those lines, so he can get used to his "new' world and how he fits into this one, now, as well as how dad and mom still fit also, just not in the same house.
hugs,
A. R.N., Energy Medicine Practitioner