How can a biological sexual orientation be defined by a social category?

I’ve been struggling with this for days, and it’s making my gender dysphoria much worse.

I’ve always heard that sexual orientation has biological roots, while gender is often described as a social construct. What I can’t reconcile is this: if sexual orientation is ultimately biological, why do we define it using gender categories instead of biological ones?

This has turned into a much deeper fear for me. I desperately want to believe that I was simply born trans, not that I became trans because of socialization, culture, or the existence of gender as a human invention. The thought that the core of who I am could depend on something created by humans, rather than something rooted in nature, is devastating to me.

If “woman” is a social category rather than a biological one, how does it make sense to call a man attracted to a trans woman heterosexual if orientation itself is supposed to be biological? What bridges that gap?

My dysphoria keeps telling me that if gender only exists because humans created those categories, then outside of human culture I’d just be male, and any attraction toward me would simply be male-to-male. I hate how much that idea resonates with my dysphoria, and I can’t seem to find a satisfying answer to it.

I’m not trying to invalidate trans people or start a political argument. I’m trans myself, and this question comes from a place of genuine distress. I’m asking because I want to understand how philosophers, psychologists, or researchers reconcile these ideas without dismissing either the biological basis of sexual orientation or the social nature of gender.