I'm not going to reply directly about the size of your sex. Instead, look at this video :
YouTube - Nick Vujicic, No Arms, No Legs, No Worries! Part 3
At some point, the guy says : "find something you really like about yourself, and that no one can deny you have, and start from there" (or something like that).
Don't look at missed opportunities, cause it's going to make you miss more things. Look at what you've got that no one else has, or at least that no one else can deny you have...