Gay, with a bf, but starting to fall in love with a girl.

I've been with my current boyfriend for 2.5 years now. Some months ago, I started amateur theater lessons and one of the girls there was kinda flirty with me. That was before i told them that I have a bf. Flirting thus subdued. Still, we get along very well.Now, about 2 weeks ago, I begun to realize I'm slowly falling for her, and I have no idea where this come from all of a sudden. I'm not even interested in girls in general.The thing is, I still love my boyfriend, I still prefer guys over girls. But what I feel when I think about her is unmistakable.It keeps me awake at nights. I'm half thinking about talking about it to either a therapist, or my boyfriend, or both.