Destination Alien Captive by Dee J. Holmes

This alien warrior will not long for his captor.

Time is running out for astrobiologist Harper Blackwell, until the sweet, lonely scientist receives an offer she can’t refuse: study the alien responsible for her terminal condition. The secretive government project promises a cure. But the massive, muscle-bound alien strapped to a table sparks an impossible yearning—how can she perform torturous tests on him?

D’tan of the Apex’ir longs for a mate to spoil and adore—but hope vanishes when he’s captured by his enemies, the Fever. Stripped of his armor, his mating instincts being twisted, he’s desperate to escape. The warrior would normally fight any male who disrespects a female, but he sees only one way out: shove his morals aside and seduce the little human studying him.

But the Fever wants him to breed with her. Worse, so does he.
And Harper? She might not be human at all…