As you scroll through your texts you notice you don't have any from your girlfriend. All of your texts look the exact same as you left it in your home world, except that instead of her name, you find a guy in its place. He has the masculinized form of your girlfriend's name and shares her last name. If you didn't know better you'd say he was her twin brother.
As you look through your texts with him it becomes glaringly obvious. In this world your girlfriend is actually your boyfriend, and he wears the pants in your relationship. In the places on your phone where you used to find dirty pics she sent you, you instead find his dick pics, and man is he bigger than you ever were. You start to feel a fluttering as you're turned on by naked pictures of a man that looks like a gender-swap of your girlfriend.
You've never been attracted to men, nothing against homosexuals, just wasn't your thing. But now looking at naked pics of your supposed boyfriend, you start to get turned on. And you instinctually start to grab at your now absent penis, reminding you that you are the 'female' of this relationship, despite your appearance still being the exact same otherwise. You guess here you're gay, or still straight, you don't really know, and frankly don't care, because right now you're turned on by your boyfriend's dick picks, and you start to rub at your new hole.