I don’t think you really fucked up. Sounds like you’re just 18 or so and have never had a serious relationship. Give her some space. Good piece of advice- sometimes you don’t have to communicate every feeling you’re having lol. You probably scared her by filling her in on the ‘actually if I’m your second choice never mind’ part 🤣 be true to yourself, that was the smart move, but telling her probably made her feel like she hurt you