Asking for some help identifying a story I read between 20 and 25 years ago (so around Y2K)

The main elements that I remember are that it featured a post-fall setting, where an all female, Borg-like race had taken over. They would attack settlements and brainwash the women to join them, and feminize and brainwash the men too. Converted males were the ones given birthing duties.

The main character had a companion that came from a race/tribe that was androgynous until adulthood, and chooses their gender.

The main character spent some time captured by the enemy as they tried to break him. They weren't succesfull, and he either escaped or was saved by the companion. At the end of it, he's still male, and the companion chooses to be female to be with him.

Not sure how much it counts as a transgender story, but it certainly had the themes. It was more of a mind control story. Been trying to find it a while and hoping somebody has an idea or clue to help me.

Much appreciated.