Why do i feel and act like that?

i started to highschool 2,5 yrs ago.before that i had a lot of friends at school (and a best friend-but now i see she was using me,whatever)and a love(he was a teacher:)platonic surely)and the summer between middle and highschool was super too,i spend the summer with hanging out as it had to be.but when the school started,i was almost alone except a girl(were still friends)and the whole cl was bullying me.next year things went the same(i had a little more friends).there was a girl which was bullying me and i heard she always does that,a trouble to the school,but she gives money to the school to not being fired(i hate this school,so she can come at 12 am -and drunk- to dormitary-she does stay there but i do not),so you see i was unlucky.this year i have a few sincere friends and im not alone and being bullied in cl(the cl has changed) but i found out i have lost my ability to make new friends.i cant trust easily.ive known as calm and silent but im not among my friends.