Being thirteen can be hard, I'm 17 and people aren't always nice to me. BUT I also have people who care and love me, and I bet you do too. If people are telling you to rot; 1) don't listen- when I came home sometimes I would call my grandma and she'd say "sticks and stones may break my bones but words will never hurt me." But I know words can hurt, and all you want is for people to love and accept you and treat you right, though you probably have people like that(family and close friends).
2) ask them if picking on you makes them feel better, ask them if they think that doing this would make please their parents and grandparents.
3)don't them push you around, stand your ground and find people(friends, family, trusted adults) ask for their support.
Listen to this song: conversations with 13 years old self by Adele
It will get better :)

Please hang in there. God is real and He loves you. I hope u r ok today.