I feel attached to my therapist, but this feels totally normal to me - I'm attached to several people in my life. It's not something I worry about. Though I have worried that he'll die suddenly as I've had several traumatic losses in my life like that.

He's totally a real person in my life, just like everyone else. For me, paying him doesn't make him unreal. (But then I've never understood the way people talk about school for example, as not being "the real world". Every aspect of my life is real to me.) I have a lot of friends and loving family members, but I look for something different from my therapist- I have a lot of grieving and trauma to work through, and I need real help with that from someone who understands how that affects the mind, and who can help me navigate through the pain of this without getting caught up in it personally.

To answer the OP, I've never felt the need to tell him explicitly as I think it's pretty obvious. He has written about attachment in his books as being a normal and natural aspect of human relationship.