Shared with a Bull by Rayann Kendal, Hedon Press

Gwen and Avery's marriage is happy, but it has become routine. Gwen misses the flirtation her friends enjoy and the thrill of the pursuit. Now, it's all work and no play.
Until her work provides a very playful opportunity in the form of a dark, handsome new employee. But, good wife that she is, Gwen denies the man's advances in favor of remaining true to her husband, though the guilt of her stolen, sensual tryst weighs on her.
Until the confession.