Late diagnosis regression?

I am a 54 year old male who has been diagnosed in the past year.

I have struggled silently all my life with the feeling of being an alien on this planet.

I look like you, I sound like you, but I am using all of my energy trying to be like you.

Since I got my diagnosis I have gone through a lot of emotions, such as being angry at myself for leaving it so long to ask for help, and angry at the education system for not helping a child who was clearly needing help all those years ago.

When I received the diagnosis of autism I was instantly relieved and felt a huge pressure lifted from my shoulders, but that has now changed to becoming more socially isolated and anxious.

I have heard of "post diagnosis regression" and was wondering if any of the community had heard of it or suffered from it?