All the Wrong Reasons by Erin Bevan

What has she done?
When a night out meant to mend her broken heart lands Christian school teacher Alexandra Mills in hot water, figuring out whose bed she’s woken up in is the least of her concerns.
Alex is unmarried and pregnant, and now she may lose her job.
Max Buchanan has been Alex’s best friend for twenty years. As the town’s most eligible bachelor, a political figure and handsome ladies’ man, she’s never seen him as anything more. But that’s about to change.
To keep his company afloat, Max needs to prove his playboy reputation is in the past. To keep her job, Alex needs a husband.
The solution is obvious—a marriage of convenience.
Now he just has to convince her.