ok the thingy gets thing sometimes in the middle ( attains some kind of hourglass deformity when not erected ) .. after someone here asked me to do so , i noticed it gets thin at the place it bends ( probarly )
I've noticed this on myself too but I think I know what it's from. This seems to be the same place where I hold my penis when I masturbate. I guess this could be why. See if it's true for you.