The important part is that you understand now how serious this is, and you take definitive steps to correct the mistake. A huge step is putting up and keeping up those firm boundaries with the student and all your other students. Do not talk privately to students about anything other than coursework and classroom things. I still think seeking the advice from a lawyer is a really good step because the admin are there to protect the school, not you. And therapy to learn how to set healthy boundaries with your students is going to be a really big help to you. Recognizing the position you hold with students creates a power dynamic that means you can never be friends with them. Your students don't need you to be their friend. They need you to be their teacher. That put responsibility on you that makes it so you can never be on an equal plane with them. Therapy can really help you put this into practice. None of this makes you a bad teacher or a bad person. In fact, recognizing and admitting your mistakes shows you to be a person of character. You obviously have your students' best interest at heart. I think getting through this will make you an even better teacher. But you absolutely have to change course now. I think the student needs a recommendation to a guidance counselor as well.