You knew you were straight before you ever had sex, right?
Yes, but only because I'd already engaged in other romantic activities with someone of the opposite sex. Still, prior to that there would have been no way to establish my being straight. As I've said time and time again, attraction establishes nothing.
Back when you were a freshman in high school you were jerking it to straight porn, right?
Ignoring the odd and inappropriate nature of the question, it doesn't matter what you find attractive or unattractive. All that matters is who you choose to be with romantically and/or sexually.
Plenty of gay people knew the were gay when they were kids. Before they had ever had sex with anyone.
They may have been aware of who they were attracted to, but there was no way to establish if they were gay or not until they acted in a romantic and/or sexual way with another person.
You're arguing in a circle here - basically what you're saying is "attraction makes you gay because it does".