I think the picture you showed is pretty damn flattering actually. You're getting a lot of positive feedback, and it's probably because you're sitting there, gently leaned back and you're letting your dick rest on your abdomen. It really shows in the girth. The thing is, I bet it probably looks a lot different to you for two reasons. First, when all of us big guys look down at our junk, there's a lot of visual distance there. Second, considering your size and build, if you looked at yourself in the mirror and let your dick hang, your overall big bodied mass may make your dick look smaller.
Either way, at the end of the day, your dimensions are ample and you know it. Good on ya!