Don't despair, sunnyside. What you're experencing is perfectly normal. Your length and girth will vary according to the degree of arousal. For instance, if you stop for a quicky you'll be one size, do some lazy edging while watching porn, you'll be a little bigger. All-out, give and take sex, you'll probably be your biggest and hardest. Quit measuring so much. And quit worrying. You're way above average and, short of amputation, you'll stay that way.