You're referring to Chapter 7 not including the Prologue - the Nole Woods one, right? - and I've caught that little typo - the "lawyer" thing. He is actually a dentist, that was a mistake on my part! Thank you for catching it! I've fixed it. (Let me know if you spot any more discrepancies. I am, after all, only human and prone to error ) And I believe you're correct on the chapter where Evan says "And I've never been with a guy before." But he has been with Nole Woods, right? I can understand where this is confusing because he seems to either be lying to Leonardo or contradicting himself...which one?
He has in fact been with Nole. That is true. But as you know now, the experience was extremely traumatic - being outed, Nole's assault, etc. I imagined Evan as one who never accepted his homosexuality or admitted it to himself because of this experience with Nole which was both his first time with a guy, and his last time (since he met Leonardo). To me, it's like Evan tried everything he could to cover up/ignore his sexuality and forget his relationship with Nole - which was basically only physical. He went so far into the closet that even he seemed to forget and disregard it all. That's why in the beginning he doesn't admit to you, the reader, that he was originally gay before meeting Leo. But he is in fact gay.
A combination of being in Spain - a foreign country where no one knows him - and Leonardo's good looks, as well as the instant, strong, powerful connection with Leonardo that makes him realize he's gay and that it's okay. It takes Leo to draw him out and admit that he's gay even to himself.