Subservient vampire queen

You happen to have an extremely rare blood type, Rh-null, which is considered golden blood. A vampire queen found you, feeling the delicious smell of your blood. She proposed a deal to you - as long as you offer her your blood from time to time, she will do whatever you want. It seems your blood type is the biggest delicacy in the world of vampires, and it gives them benefits - health, power, a better look, and more. So, give away a bit of your blood every few days, in exchange for eternal gratitude and servitude to the vampire queen, who will be at your every beck and call. It would be such a waste to refuse.