BBC is one big myth, perpetuated by porn. Data has shown that ethic origin has no significant differences in erect penis sizes. You guys look pretty average. Most guys are. The only real difference is black men are often showers, while white guys tend to be growers. If you lined up 100 erect black men and 100 white men, each group would have around 15 guys each that were 7" or longer.
Those who come to sex forums often end up thinking that 7" is pretty average. That's not true. Average is 5.3" erect. You see mostly bigger cocks on sex forums, as guys with bigger cocks are more likely to post pics of themselves. Guys that never post pics tend to exaggerate their size. As the focus of this site is big cocks, you're going to see more of them here. Average always was and always will be 5.3".