Habit (1997)

Sam (Larry Fessenden), a down-and-out New Yorker who is grieving over his father's death and has just broken up with his girlfriend, is lost in an alcoholic haze. When he meets the seductive Anna (Meredith Snaider) at a party, he immediately falls under her spell. Soon, Sam is pulled into a sporadic relationship with the mysterious woman, and their trysts increasingly involve blood being shed, slowly affirming his suspicion that he may be dating an actual vampire.