The Inevitable Trilogy Series by Jason Letts

 Every choice is played out in a world unto itself, and so the only Nathan who needs to be saved is the only one who can't be.

A supernatural spirit holds all of these worlds together, bending fate from her place outside of time. When eighteen-year-old Nathan Wheeler sacrifices himself to provide for his orphaned sister, this entrancing spirit goes back to when the death of his mother forced him to quit college and attempts to make his life better before his inevitable death. But for all she knows about the future, assuming human form is not as easy as she thought it would be, and getting close to Nathan comes with consequences she could never expect.

 In the second book of The Inevitable Trilogy, a new threat puts Nathan's life in grave danger. Coming to terms with his predicament proves a tall order for Nathan, troubling his family and his girlfriend. It’s up to his sister and the magical spirit who came into his life to save him, and to do so they’ll have to venture beyond what anyone thought possible.

 After a single mistake threatens to separate Nathan and Apoxy forever, the star-crossed pair must find a way to beat back their own looming mortality.