I just wanted to add another "you're not alone".
While I have gotten to a place where I don't frequently verbally beat myself up, every once in a while I slip. My husband once told me "Those aren't your words, that's not really what you think." When I asked him how he could know that, he replied "Because you'd never say that about someone else."
Perhaps you need, not to pretend you're someone else, but to treat yourself as though you were someone else. I'm guessing that you are a very supportive and encouraging person to everyone in the world except you.