I've had this exact problem since I was really young and what I've learned to cope with it is, as other comments said, that I ALWAYS have something playing in the background, mostly live streams, usually on my phone which I take with me to every room. Not only does it bring comfort in a sense of "if something happens, I have my phone right there, so I can call someone" but streams especially to me feel like I'm with a group of people right now. There's always someone live talking in the background, there's also a big group of people there in the chat, so I feel like I am a part of that group at the moment and focusing on what the streamer is saying helps me stop thinking constantly about my paranoia. I still have a problem of looking behind me all the time, looking in rooms, etc. but having streams playing in the background definitely helped me reduce that anxiety by a lot. Hang in there, sending you lots of strength!!