Duty Bound (Duty Series #2)
Sandra McGregor

Since he knows his body better than Victoria, and since he buffed it up once before, he decides to augment her therapy program with additional workouts of his own.
When two headstrong overachievers butt heads, there can only be fireworks, especially when Victoria discovers that Mason has been working behind her back—and effectively lying to her.
Despite his growing feelings for her, she stood in the way of his getting back to his squadron, but he never intended to hurt her and now he knows he has blown any chance of them getting together.
Victoria is in a dilemma. She can no longer claim responsibility for his rapid improvement, so she must now decide whether to report his actions and risk ruining his career or try to find an alternative answer to the issue—an answer that just might get him out of her hair, but is that what she really wants?