I feel ya. I was getting an AIDs test, and I'm STD free thank gawd, but she kept asking me when the last time I had vaginal sex was and I was juts like I have only had oral sex this year. She was just like well i just assumed you were heterosexual and liked men, so sorry if I made you uncomfortable. And I was like No I am hetero it's just i've been unlcuky this year and have been prudish.
One time I had to disclose cause my legal name was on the document and then she put down I'm a transsexual, well transgender, which I hatehatehate being called, I'm not transgender, this has nothing to do with gender, but it was awkward. I hate disclosing. Even then, a couple days later I called back and they kept saying you have to call this_____ place. And that was werid since it's an all women's health center OB/GYN other women's issues health stuff. And when I went to the doctor I had to disclose to I was dressed male-ish and she still asked about my vagina at one point, like she forgot. I mean I know it's lucky that I am so passable (but wish I was pretty and passable) but they're two different things.
But yeah, sorry for the tangent, I totally get not disclosing. I don't ever unless I absolutely have to...and even then I only own women's clothes so even my andro ones show my figure off, which is in no way male. And never has been. I got stretch makes everywhere, well, in all the areas you expect a woman who went thru puberty has them. It's so odd.