[private joker]

Zeebo -- it has nothing to do with penis size. Girls have trouble relaxing when they're having sex for the first time, because they're not used to it. You just have to practice a few more times. Just because she can get a tampon in doesn't mean she's ready to accept a penis. Take it slow and let her gradually relax. It will work best if you're on your back and let her sit on top and control the speed and depth of penetration.