No, that's not what I'm saying. The blood that's pumping through their veins is from the blood they ingested (yes, here's where the logical fallacy of Vampires comes in), but that blood doesn't continue to recirculate and regenerate, like ours does, that's why they have to keep feeding. The blood only lasts so long. If they were to... get it up, so to speak, that would take away from the blood that was being used to temporarily regenerate the rest of the body, so the vampire would wither away, anyway.
In order for one to have sex, they would, basically, need to be feeding while they're doing it, so as to keep a constant flow of blood through the body, to make up for the blood that was ... presently being redirected.
And yes, peeps, there's ton's of sex in True Blood, and in Buffy, and there was in the Twilight novels as well.
I'm just saying, logically.... If one were to follow the true rules of vampire as a supernatural being... there wouldn't be any boy vamp nookie.