Don't know what to do!

Ok so long story short:

A year and a half ago I made it known to my best friend and myself that I am in fact Bi-Sexual. I've always only ever been with guys as I never found the right girl.

Fast forward a year later: I now have a boyfriend and I'm so in love with him, he's everything to me BUT I have this SUPER strong desire to be with a girl.. I've always been way more attracted to girls and the last four months I've been really struggling with it. I really want to experience what it's like with another girl but it makes me feel guilty. I don't know what to do 😞