I may be misunderstanding here but it sounds as though you want him to understand how you feel about your therapist and therapy, is that right? Do you know why it's so important to you for him to understand? It is good to have support and understanding but those are your feelings and your transference, it might be really difficult for him to understand, as he's not the one feeling it, however hard you try to explain.

Also, as Hazel mentioned, he might feel uncomfortable or even jealous about you developing a strong relationship/feelings with another person. Perhaps he has attachment issues and is frightened of losing you?

Mine sometimes asks, I used to feel obliged to tell him but now I don't so much - it's my therapy, my journey. He can also be quite scathing & angry about the fact that I go, because it's something separate to him and us I think. So I find it best not to talk about it too much... unless it is something useful, that can help with parenting or our relationship.