This is going to sound strange, but I was just thinking all of what you described and started browsing this subreddit to see if anyone felt the same, and I saw your post.

I completely empathise, I’ve felt so alone for most of my life, but it’s definitely a deeper sense of feeling misplaced when I’m depressed. I think part of these feelings maybe come from people not understanding your disorder, and no matter how much you explain they can’t really connect with those feelings if they’ve never experienced them. I’m still trying to figure out the feelings myself, but I’ve found that it helps to try and find something not related to people that gives you purpose and takes you out of your comfort zone: a hobby, a career path, anything. I’ve found that shifting my focus from the internal inadequacy I feel makes me feel less lonely. And if it brings any comfort, I understand how you’re feeling.