Why can't I cure my diseases?

I have Skyrim for PlayStation 3, and in-game I have contracted 9 diseases.

Recently one of them has made my screen get considerably dark and my health drain. They don't appear in my active effects and no matter what I do, for example, drinking cure disease potions or go to a temple or shrine, they don't get cured and disappear.

I don't know what to do, and help would be greatly appreciated

You have become a vampire. You can cure your vampirism by becoming a werewolf or doing the Rising at Dawn quest. To start the quest, ask any innkeeper for rumors as a vampire.

In the future, don't go more than 3 days while infected with Sanguinare Vampiris, which you get from, big surprise, vampires.