I have, since I can remember felt a heavy sense of guilt. I feel guilt for everything. Watching the news causes me great pain, and I feel guilty for all that I cannot help.
Like you, I always shy away and try to blend into the background... However, it was much worse when I was younger. I first attributed this to Catholicism, since that plays alot on feeling and repenting for sin. However, although we did practice it much more when I was young, it was never to an extreme... Not enough to cause perpetual guilt.
Then, my ex boyfriend once told me that maybe it was an extension of the poor self image I held of myself. Granted.... I have struggled with BDD for many years, but I still don't think that this is the root of the issue.
I am also sensitive to others, and have just always felt too much. So much that if I hear a nice song in the car while driving, I cry.
I can't watch scary movies or gore because its just too much for me. All emotions are too much. It's like they are too big for me to handle, especially the guilt. This guilt has greatly attributed to my depression. Its very frustrating. I don't surround myself with loads of people because drama and negativity really affect me too. Somehow, I think, its all related.
Anyway. What has helped me is that I now try to focus on the things that I DO have control over. I volunteer and read in my free time. And I chose to be very selective with those I let in. I'd rather solitude that is at least somewhat familiar.... As opposed to the all consuming feelings of having to be around people for the sake of fitting in.