I think you just feel a little uncomfortable that everyone else isn't enjoying the clothing -optional aspect of the beach you attend. Its not that you're uncomfortable with your naked body in others, its that the people around you aren't clearly as comfortable. Seeing your body, which i'm sure is a signt to see is out of place with the rest of the environment. I suggest you go to a nude beach where the majority of the people are nude too.
What do you think of that?