I also had this kind of experience in secondary school, and mine was so terrible that when I got to the university, I didn’t mingle with friends. I only attend lectures, and if I’m not clear about anything, I meet one of my coursemates and ask. No friendship, just a coursemate relationship, because what’s the essence of having a friend for six good years, doing everything together, eating, buying clothes together, and yet we didn't know each other’s true behavior.
I'm sorry you went through that. Being the same case with mine, I can tell just how it feels. The fact that it made it hard for you to be friends with others even in the university goes on to show just how much it affected you.
But I hope you have good friends now right???
Yes, I now have friends who are like family to me.
That's amazing 😍