Jealousy

help! i’m currently in a teen relationship with this guy(he’s two years older than me) and he goes to a different school. he has a lot of friends, a few of them being female, but the thing that bothers me about these girls is that most of them are his ex’s. he’s also friends with the “f***girls” and it drives me crazy! i trust him 100% but i’m scared he’ll cheat on me or just leave me for one of them.. when he talks about them like if they were messing around it just gives me chills.. anybody else or any tips?