How do you think your self image matches up with how you really look to others?

When I see photos of myself, they always surprise me (as in “wow there’s no way that fat cow is me!”). I never look the way I imagine myself when I’m not looking at a photograph or a mirror. What I see in the mirror, however, is totally different than what I see in photographs of myself. Looking in a mirror is a different experience every time too and I never know quite what to expect. It’s not like looking at a totally different person every time, more like some days I like the way I look, and sometimes I’ll hate the way I look. Do you have similar experience with your self image? Am I just insane?