Your shaft girth will always be a bit bigger right before you reach a 100% erection. I don't know why. When your dick becomes completely hard, and "locks up", the shaft girth does decrease slightly. My girth always looks thicker when I have a semi-erection.
This might be because almost all of the blood that goes in, is in it. And the length isnt all there yet, so it expands the girth momentarily. Until the muscles tighten up all the way to give you your full length.
