Feeling unfeminine when dating women?

For context, I have been dating men since I was 16 and began social transition. I have had very few encounters with women, limited to kissing and cuddling. Twice now it has happened that I grow close to a cisgender girl and begin to feel attracted to them. It is a strange feeling and whenever I describe it to friends or family they are taken aback, since I have been so decidedly heterosexual for the most part. The feeling is compounded by a change in self-perception. I understand the existence of lipstick lesbians (this might be going too far, I am unsure whether I actually see myself being with another woman) but the two times it’s happened I begin to see myself as more masculine. It makes me doubt my feminine identity somehow. I see my body differently. I approach them differently. I flirt in a kind of masculine way. It really makes me feel strange, I never behave like this otherwise. Last time it happened, the girl was especially short, and I started to see myself as her protector, and even suspended my hormone intake momentarily (not recommended, of course). I am, in any case, comfortable with fluctuations in my presentation (I just got a pixie cut after having a long bob for years, I mostly don’t wear makeup save for lipstick, I wear blue jeans often; some time ago I only wore skirts) but this makes me very uncomfortable. It is one thing to see myself as a sort of tomboy and another to see myself as a less-than woman. Of course I can’t help who I am attracted to, but why can’t I stop this strange feeling?

Is this some form of internalized heteronormativity? Does this happen to anybody else? Do you know of a way to reason with the feeling? What might it all mean?