Oh sweetie, my heart is breaking to think of your baby struggling like that. I can't imagine what it's doing to you.
Even though my son was much older (15) when this happened, he struggled a great deal. Still does sometimes. When I asked him recently what helped him the most, he said it helped that I always seemed around and available to talk. He said the fact that I encouraged a relationship with his dad and that I tried to keep life as normal as possible for him.
But the thing that really helped was that I held it together. While he knew that I was sad, I rarely let it interfere with our life together. He said that he looked to me as his touchstone - if I was ok, he felt ok, too.
So, Grr, my friend Mach is right, you need to handle this. You might want to make new routines with your son. Get his input. Try to start some new traditions between the two of you. Make a plan on your day off and put it on the calendar. Get him excited about looking forward to it.
Grr, he is looking to you to set the tone. Be his touchstone.
In my opinion, I would not move in with your h. Your son will be watching to see what is going on between you and if it is temporary, he will have to deal with the news all over again.
You and your h might want to go to parenting counseling together to see the best way to handle this.
Show your son that while life isnt fair sometimes, it does not mean that you give up. Show him how to handle what is thrown at you with dignity, strength and courage.
