Hi. I haven't diagnosed with Autism but I have felt a lot of the same things that you talked about. I have PTSD and social anxiety and bad experiences with people so that is why I am more comfortable at home. Maybe you can talk to a therapist in a video call. It is more comfortable for me to do it at home than going in person. I also understand what you meant by Selective Mutism. I recently learned that it existed and I think I at least experienced this as a kid. In school people used to make a big deal if I ever smiled so I stopped smiling around them so they would not all look at me.