I have a boyfriend but I like girls?

So I have a bf. we've been together for 3 months. But before I started dating him I was with this girl(my first girl experience). I fell for her but she was messing with my head so I sopped talking to her. Anyways I really like my bf. but I think about girls more than I should. I really would love to either hookup with a girl or have a girlfriend. What should I do? I don't wanna break up with him but I really am more interested in girls. He knows that I'm bi, but he's very insecure so I don't think that he be okie with it. Although when we first started dating he told me I could and he wouldn't mind. But now I feel like he will. Please if anyone was been in the situation before or has any advice please tell me! Thanks (: