Divorced. My fault, and cant move forward

[Mrs D]

So I had no communication today with ExH. Which is a good thing, I know. Its easier when you are so busy at work that the thoughts of him that enter my mind don't last long. Took my son to the truck pulls tonight at the fair. We had fun. He came home, asked to call his Dad, and he doesnt answer. My son leaves a message, but I can tell he is hurt. This happens almost every Tuesday and every Thursday. How can I protect him from this hurt he may be feeling? I have said something to ExH before, explaining that his son should be priority before the GF. Its a two minute conversation. When he has our son, I go out of my way to make sure I tell him goodnight. It just frustrates me the look in his face when he has to leave a message. IDK. Maybe Im wrong his child should come first?