Just going by the size of your thumb there, yes you have a big dick, it's just a really bad way to take this kind of photo. I'm not sure why you're so opposed to just holding the tape measure on the top of your dick (you're already holding your thumb there.) I don't think it's adding nearly as much as it does in my demo below, I'm just including it so you can see how a shot like this isn't reliable.
Here is a basic example of why this sort of photo is a little dubious:
http://www.lpsg.org/members/shannonh/albums/photo+analysis/581164-so-two-pieces-of-paper.html
So two pieces of paper, one on a table, one in my hand. The one in my hand looks a lot longer, but in fact, they're both 8.5"x11" pieces of paper. Except: the one on the table is folded the long way (11") and the one in my hand is folded the short way (8.5). I didn't even use as much trickery as I could -- my camera was still pretty far from the top paper. If I move the top paper even closer (or use a different camera with a wide-angle lens) the top can look almost twice the length of the bottom, in spite of being far shorter.