Girls with boyfriends 18+ and your still underage

I've been with my boyfriend for almost 2 years , he's 18 next week and I'm almost 16, he's my first relationship and I do trust him and everything but people I've spoken to before him made me have major trust issues, I do trust him and everything but I know what girls are like these days. They don't care if boys have girlfriends.. I always get scared he's going to find someone better than me. We've known Eachother for 3 years and always I've had a thing for him, is it normal to feel like this? And do any of you girls have the same feeling? Although I know he won't go clubbing with girls, I'm dreading him going out and drinking with the boys, especially the ones I don't like and don't trust. I can't help but be scared. I won't stop him from going out but I don't wanna lose him. Is this feeling normal?😒