The Avebury Legacy (aka Advent) (Vampires: The New Age #1)
by Natasha Duncan-Drake
Nate is a vampire hunter infected with vampirism, Lexie is the witch who infected him while saving his life. They have less than six months before Lexie's magic can no longer delay the symptoms and keep them at least partially human. The legendary Avebury ritual is their only hope of a cure, but the relics needed to perform it were hidden long ago and finding them may take time they don't have.