Always knew

First, off I know I am a bisexual and right now I am in a straight relationship, but no one obviously knows. I have known this since I was like 10. I have always loved to look at girls and I watch girl on girl porn. It definitely arouses me more than sex with my boyfriend. In order for me to have an orgasm when he gives me oral sex I have to imagine it is a girl doing it. Then I have an orgasm. Also, I have had an sexual encounter with a girl before, but of course he doesn’t know this. I feel like I keep this secret, because in my family this is not accepted and I am afraid I will lose him and I really do love him.