Blood, Moon and Sun Series by Amber Kell

Randall is a poor medical student looking for a job. When his roommate Darren tells him all about an easy position with the company he works for, little does he know that he's about to become the favorite blood giver of the toughest vampire in town.

Randall has a bad feeling about the upcoming Samhain festivities. A gut-wrenching foreboding that something is going to go wrong. When he's taken over by the spirit of a dead fae king, he learns this is just the beginning of his problems. Now with the ability to access powerful abilities, Randall finds it difficult to submit to his vampire lover. Because while Randall the medical student defers to his mate, the fae king attempting to take over his body will bow to no one.