I never feared it either. Guys who have this crazy "Does size matter?" mental complex is clearly insecure about themselves and it's really sad. Why even worry about a crazy theory like that? Just be happy that you are with someone who you care about. She sees that you are sure of yourself, you are not a headcase, she sees that you don't have any insecurities about your dick, and you don't waste time believing in ridiculous sexual stereotypes and urban myths.