Most people have at least one body part that causes them to feel insecure. I have such an insecurity too and I have always kept it secret. Two people in the entire world know about it. I would have shared it more often if only I didn't know that whenever I do share it, people tend to laugh and dismiss it.
My insecurity has to do with the shape of my head. (And no, it isn't funny.) It is a very weird shape, folks. Of course, I'm lucky in that I have quite a lot of hair, so I just cover it up. The only hair-style that manages to cover the weird head shape successfully is having my hair down, so I hardly ever wear it any other way.
More often than not, people have a scale in their head against which they measure whether one's insecurities are considered reasonable. Everything that has to do with weight takes pride of place on the insecurity scale. It is considered absolutely normal and even necessary to be insecure about one's weight being too high, too low, too moderate, etc. Noses and ears also make for acceptable sources of insecurity. The eyes, cheeks and foreheads are, however, much less acceptable in this sense. (Have you ever heard anybody say they were insecure about their forehead?)
I'm actually seriously bothered by the weird shape of my head. Nobody takes my insecurity seriously, though.