Backwards to Oregon (The Oregon Series, #1)

"Luke" Hamilton has always been sure that she'd never marry. She accepted that she would spend her life alone when she chose to live her life disguised as a man.
After working in a brothel for three years, Nora Macauley has lost all illusions about love. She no longer hopes for a man who will sweep her off her feet and take her away to begin a new, respectable life.
But now they find themselves married and on the way to Oregon in a covered wagon, with two thousand miles ahead of them.