My first question is whether your therapist is actually a medical doctor, a psychiatrist. That would be more common if that is the case. Otherwise, it does seem unusual for a therapist to insist on titles and last name.

I do call my pdoc Dr. M____, but all of my therapists were on a first name basis. The reality though is that I actually rarely use his name when talking to him. Generally when I use his name it is when I call and speak to secretaries to make appointments. In those cases, what name I use actually depends on who I'm speaking to. If it is the usual secretary, I use his first name, but if it is someone who doesn't know me, I say Dr. M (he's a PhD.).

Do you really actually use your T's name that much?