What could I do about this

I tried to get more evidence that these 2 boys are bullying/harassing me but when I went to check the messages on Snapchat they were gone. One of them was about how one of the boys wanted to have sex with me really bad. I have people that can defend me with everything that happened but they normally stay out of these situations and the others are his friends and they help him with everything. This seriously worries me because they get people to gang up on me, try to embarrass me, sexually assault/harassed me, and bullied me most of high school and I want to get justice for what happened to me. But it’s hard since I have very few evidence of it, there could of been more but I don’t know what to do now. I’m scared as hell to go back to school because I don’t feel safe there. My problem started with the 2 boys specifically then it turned into people making groups to try to hurt me.