Dirty Saint (The Grim Saints MC 1) by Rowan St. George

Willow left her small town as soon as she had the chance. Yet, her sister derails that plan by asking her to come home for the sake of the baby on the way.

 Willow never expects to stay or to be caught up in Jamison Walker’s orbit. She is not looking for trouble, but a love from the past may incite a war. Willow will need to decide what she truly wants.

Jamison aka Ares
Ares has been groomed to lead the Grim Saints Motorcycle Club. He's an alpha who wears the Prez patch and has the respect of every member in his club. When Willow comes knocking asking him for favors, he only plans to show her how hot they can be in the sheets. Time goes by and he starts to wonder if it was all a game, but one thing the god of war knows for sure is that he will be the one left standing.

Can Willow and Ares figure it out long enough not to kill each other?