Oh my God, LIMP, shut up. Shut up, shut up, SHUT UP. I cut your letter by four-fifths and it's still fucking interminable. If you've managed to land a girlfriend who can put up with your florid rhetorical style—you don't by chance own a comic-book shop in Springfield, do you?—you should count your blessings and suck up the angst about the size of your dick.
I'm sorry, LIMP, but if your girlfriend's assurances about the quality of your sex life and her preference for average-size cock isn't enough to set you at ease, nothing I can say in this space is going to do the trick. I'm familiar with dudes like you—insecure bags of slop always harping away about the size of their dicks—and there's just no debuttressing your fears. Even if your girlfriend was a virgin when you met and yours was the only dick she'd ever laid thighs on, LIMP, you would still be paranoid. You would send me letters insisting that your girlfriend could never truly be satisfied with you, having never experienced the substantially more girthsome appendages of males lucky enough to be more impressively endowed blah blah blah.
Stop obsessing about your dick, LIMP. Just stop. Your dick is your dick and obsessing about size only makes you miserable. And verbose. If size were all that mattered, Ron Jeremy would be People's "Sexiest Man Alive" every fucking year instead of, you know, those mouse-dicked motherfuckers George Clooney and Matt Damon and Brad Pitt. If knowing your girlfriend used to be with a guy who had a huge dick—with him three or four times a day, for five long, pussy-punishing years—is more than your fragile ego can handle, do your girlfriend a favor and dump her now.