Why don't I feel like a girl?

I’m not sure how to describe it but a lot of the time I feel sort of…genderless. Or, like, ambisexterous. I don’t know. Sometimes I feel big and “manly” (I’ve been told I’m not and I’m only 5’3’’ and 140lbs) and then sometimes, very rarely, like when I wear a dress, I kind of feel like a girl. But most of the time I’m just a blob of human. Does anyone else feel this way or am I waaay overthinking my existence/sexuality?