Kate, I used to do the same thing in pictures (not smile 'cause of my gapteeth). But I finally decided fuck it, I'm gonna smile! I hope आप get to be comfortable enough with your smile to दिखाना it off someday. :)
आप have average looks, your not strikingly beautiful but then again most people aren't including myself. I think people (again myself included) tend to base their looks on मशहूर हस्तियों and people who are for lack of a better word are और attractive, so we feel down about our selves and think we are ugly द्वारा comparison. But that's like being mad at yourself for not having a million dollars like someone your own age who inherited it, its out of your control, the best आप can do is be happy your looks aren't below average and just live the best life आप can.
On a side note, I don't want to say आप have to be happy with your looks if आप don't want to but आप do have to except them. आप can mold them to be और appealing (to yourself) because in the end if आप don't think आप look good, anybody else's टिप्पणियाँ will be meaningless to you.