I think the same thing about myself. I've heard it's because when we see ourselves in the mirror our image is flipped, and when we see ourselves in a picture we are not flipped, and we are not used to seeing ourselves that way. If it helps I think you look pretty good in the picture in your profile.
I think that no one can ever really say they know what they look like. We all get fooled, so I guess the moral of the story is believe what you think you look like and go with that. Looks matter, but not as much as you would think. :)