What caused my social anxiety

Been feeling like an “outcast” in school ever since I was 12. I’ve been treated such a way and other peers were aware of it to the point where some kids would take that as an opportunity to mentally bully me. All kinds of words were slandered towards me, from body shaming me cause I was naturally very skinny to being racist cause of my darker skin tone, these things have caused me to be extremely self conscious about my appearance till this day. A few of the stuff that my so-called friends would call me were basically all sorts of words mocking my appearances in every way possible. I had endured all that in just 1 year. But at such a tender age, it didn’t get to me as much cause at that time I was naive and never saw all that as “bullying” and instead I thought it was normal for friends to say such things to each other although I knew I got it far worse than anyone else. The fact that the rest of the kids knew that I was one of the main bullying targets made things harder for me cause they would work together to give me a hard time without being caught by any discipline teachers. One day, I even got the strings to my bag cut off while I was at a dance practice in school. In that same week, someone poured maple syrup into my bag. Keep in mind that I had a test on that day. I remember going to the toilet to wash my pencils during the test cause that person made sure maple syrup had even gotten into my pencil case, and that meant that I had to spend extra time washing my pencils instead of answering my test paper.