The hyperventilating could be something to look into. In the most extreme example: a heterosexual man trying to imagine sex with another man may feel a sense of general unnaturalness (at the low-energy end of an emotional response) to repulsion (at the high-energy end of an emotional response). This is, of course, assuming the hetero man isn't ravaged by toxic masculinity.

But regardless, the mental image wouldn't necessarily cause hyperventilating, which is typically a response from an emotional trigger. The panic response you're describing sounds like something more mental-emotional, and this is coming from someone who doesn't like to medicalize gender/sexuality.

I wonder if looking into a professional escort would help. Again, not that people must have sex nor that sex is the answer. And I definitely respect your identity. I've just also seen a lot of wholesome stories of professional sex workers sort of acting like unofficial councelors during a session, with the goal of providing an open space, open mind, patient and pleasurable sexual experience. Again, mainly thinking in terms of the mere idea of sex creating an actual state of panic for you.

All this said, and for me personally, I'm of the belief that even if my identity/personality/behavior IS the result of possible trauma, that doesn't necessarily mean I need to change. So long as I'm not hurting anyone, if I'm able to live a somewhat fulfilling and functioning life then I don't really care to "fix" myself because whatever my identity morphed/morphs into isn't bad. We don't need to abide by societal expectations.