Fun fact! The reason why you look great in the mirror and weird in photos is that everyone's face is slightly asymmetrical. You're used to seeing a reverse image of your face in the mirror. Because it's the face you've grown up with, you're familiar with it and you like it. Photos are one of the only times you'll see your face flipped the other way, and it will look weird to you (there's also the fact that cameras seldom capture light and angles in ways we're used to). Try taking a webcam snap and flipping the image back and forth, and you'll get the idea. It's nifty!
I’ve known that your face is slightly asymmetrical, along with your entire body, but I didn’t know that slight difference affected the outcome of pictures. That’s really cool to know. Thanks!