I've Been Sexually Active With This Guy For 3 Months

I've been sexually active with this guy for 3 months now, but his penis is 14" long so its never has gone in all the way in my virgina. I'm extremely wet when we have sex, but still can't get it all the way inside of me. Help. He says that he never been able to insert his penis all the way with anyone before. I want to
be the first. How can i get it to fit completely inside of me?