In a relationship but questioning

I’ve been with my boyfriend for 4 years. Since high school. I love him a lot, don’t get me wrong. I’ve just been questioning my sexuality for the past few months. I used to say I’d only date certain girls, one who fit a specific type I guess. That’s still true but it’s only recently that I’ve admitted to myself that I’m not straight. There’s actually so many girls that I’d be with. There’s so many guys I’d be with. There’s girls and guys that I’d be with at the same time. But I feel like since I’m in a (straight) relationship, my feelings are somewhat invalidated and could even be wrong. I don’t want to cheat on my boyfriend but I’ve also never experimented with a girl. The most I’ve done is drunkenly kiss my best friend. I feel like I️ could be missing out on exploring my sexual identity because I’m too afraid of leaving my boyfriend. I don’t know.