Parallel Desire by Deidre Knight

On a mission of vengeance, time traveler Scott Dillon finds himself marooned in the past-and risks disrupting the entire universe in his quest to destroy the warrior who killed his wife and unborn child. A never-ending passion for Scott lures Refarian medic Shelby Tyler to Texas, but the man she finds there is nothing like the man for whom she once cared. Reeling from his loss, Scott has lost himself in drinking and brawling. With her body, Shelby will lift him from despair. And with her heart, she will help him discover a part of his soul he thought was lost forever-and the devastating truth behind the murder of his wife.