When it's your own child, it's so heartbreaking. Children, even as adults, do not understand what parents go through for them.
Just before I left the JW's for good, I read Dr. Wayne Dyer's book, Your Erroneous Zones. It's about dealing with negative emotions and putting things into perspective. He talks about how people feel when their mother does not love them. He makes the point that it is no reflection on you, and it's better to forgive and accept what is. No, it is not easy.
What is called for now is patience. Just be there for your son. He does understand that you are there if he ever needs you, right? That's really all you have the power to do.
Go out there and make a great life for yourself, and one day, out of the blue, he is likely to show up because no one else can take the place of Mom.