My experience is similar to your own weatherman3, but having worked as a photographer I know how easy it is to make an average sized cock look huge - it's a matter of making sure the cock is the nearest object to the lens, and a wide angle lens exaggerates the effect. Your 6" is at least half an inch longer than average so, like fortiesfun says, you have nothing to worry about. There are other factors that make a guy's cock look bigger:
*An average sized cock looks huge on a little guy, but small on a tall guy.
*An average sized cock looks long on a thin guy and short on a fat guy.
*A trimmed or shaved area around the base of the cock makes the cock look longer. *As long as you perceive yourself as having a small penis you will project this idea and people will buy it. Once you cotton on to the idea that you are actually quite well endowed you will present your cock to gf with more confidence. That will definitely make it seem bigger to her than if you present it apologetically.
Lastly, I'd like to pick up on your initial point:
*There are a good few very well hung members of LPSG, but there are a great many more who are of small or average endownemt, a few of whom pretend to have huge ones. Some have even been found to be using pictures of penis' not belonging to them. Really big cocks are actually quite rare - even here.