What should i do? I’m really frustrated

There’s this guy at school who I’ve been friends with since he transferred. He’s really sweet and i wouldn’t hesitate to call him my best friend. I wouldn’t say i like him like him though.. anyways recently i found out that he’s talking to this other girl.. and she’s super sweet and i can’t really find a reason to get mad and i don’t know why I’m getting jealous, but i am and it sucks and I’m really frustrated. Please help