Sorry but it appears you have some major confusion. There are creatures called Ash Vampires that work for Dagoth Ur. They are NOT real vampires and you can NOT contract vampirism from them. You certainly did not catch vampirism in the Ilunibi (aka Carcass of the Saint) near Gnaar Mok. You got corprus disease there because the Ash Ghoul curses you with it. He doesn't even need to touch you. Even if you kill him with a bow before he can open his mouth to speak you will get corprus disease from that quest. The difference between real vampires and the so called Ash Vampires is explained to you by reading the two books I mentioned in my first post and by talking to people about it. The creature with the tenacles coming out of his face and casting poison, lightning and other spells at you is called an Ascended Sleeper. They have nothing to do with vampires. They also work for Dagoth Ur and are next in line after the Ash Vampires. All of the Ash Vampires and some of the Ascended Sleepers and Ash Ghouls have personal names (all beginning with Dagoth).
SPOILER: As far as I know there is only one vampire on all of Red Mountain. He is an extremely powerful character who lives a cursed existence in a tomb. One of the deadra gods put a curse on him that serious drained his powers. He wears a full set of ebony armor and will attack you on site if you are not a vampire yourself. He is fairly easy to kill at this point. You may have contracted vampirism from him. If you did you do not belong to any clan. If you are a vampire already he will ask you to do a quest for him to regain his powers. If you do this quest he will be extremely powerful again and attack you as soon as you've finished helping him. But you do gain a neat shield for doing the quest.
Another SPOILER: You can go into Ilunibi cave BEFORE getting the quest. If you do you will NOT run into the Dagoth Gares guy. Search the final shrine area carefully and loot it. The two best guantlets in the whole game are hidden behind some objects. I'll let you find them.