Navigating Gender Identity in a Heterosexual Relationship

I recently got in a relationship with my boyfriend (he’s straight and cis) and I (think) am Pansexual he knows it but he doesn’t really know what my gender is he’s never asked and I guess he’s always assumed I’m a girl we also don’t really talk about it much I’ve always identified as nonbinary but recently I really don’t know what my gender might be. I’ve always leaned to appear more masculine and is usually feel more masculine but recently I’ve felt more feminine and like being more feminine, I really don’t know if it’s because I’m in a relationship that looks hetro and cis and maybe that’s making me feel that way but I don’t know I want to talk about it with my boyfriend but don’t know how to because I love him a lot and don’t want to break up with him because he’s straight and well I don’t know what I am.