Bisexual. Any help?

So I'm bisexual. I've been in a serious relationship with a guy for almost three years. He's the love of my life and I can see myself spending the rest of my life with him.
​But I miss girls. I miss having sex with girls. I love sex with my boyfriend. It's amazing. But I just don't know what to do. I hate fantasizing about girls. I miss sex with them.