So, it seems like your SO is experiencing some issues related to his anxiety, and is dealing in a less than optimal manner. (Obligatory Not a Doctor statement)
However it does seem like he might be somewhere under the Aro Ace umbrella by your description.
You mentioned doctor, is that a psychologist/psychiatrist? Because they don't seem very supportive.
There might be no easy way to bring up the issues in the relationship, and it sounds like he needs to make some more progress.
It could beneficial to get him to speak with another Ace person, face to face.
Or (and this is a risky method and not recommended) just start sending him ace memes that don't flat our say they are ace memes.
Oh, and please be safe and have some garlic bread.