Your past did not ruin your life! You were only 11! You were a victim of child abuse, not a willing or knowledgeable participant in sex. In the U.S., 11 is well below the age of legal consent. (I don’t know the law in Barbados but age 11 is a child as far as I’m concerned, regardless of legalities.) You deserve compassion and support, not bullying.
Your parents could confirm whether the principal really did put something in your record. I hope that is another nasty rumor, not fact. I’m not a lawyer so I can’t give you legal advice but if there is something in your record I do think your parents might want to consult a lawyer about your rights to privacy about something that happened to you as a child. If the lecturers are participating in the bullying, I hope your parents will insist that it stop.
As for your cousin and so-called friends: You need a better class of friends. I suspect “Jyl” keeps bringing it up as if she had no part in it because she knows that she and her brother are guilty of doing something terrible to you. She rationalizes it by shifting the responsibility for it on to you. By doing that, she doesn’t have to face her own guilt — and she is continuing to abuse you.
It’s asking a lot of you, but I hope you can find the strength to stand up for yourself. If someone bullies you about early sex, you might say something like, “I was only 11 and was taken advantage of by people who were old enough to know better. I trusted them and they abused me. That’s not something to bully me about.” If they don’t quit, avoid them if you can. Get adults to help you. Do consider going to another school and making a fresh start if you think that is the only way to get away from the bullies. Taking care of your emotional well-being is more important than trying to change them.
You are no different from the many, many other people who have been victimized as children. People do recover from abuse and do create good lives for themselves. You absolutely have a future — as long as you refuse to accept the opinions of toxic people. You will get a job based on your education and your skills, not on rumors about something that happened to you when you were a kid.
Being bullied is very, very difficult. You might appreciate having a therapist to talk to about how to handle “Jyl” and the bullies and how to hold onto your self-esteem in spite of their horrible behavior.
I wish you well.