your gonna have to feed to suppress the Vamprism.. find a sleeping NPC, and you should have the option to feed..
after feeding, it should revert you back to stage 1 vamprism, and NPCs won't attack you if your only stage 1 (they only attack at Stage 4.. unless you have the dawnguard DLC, then they will not attack at all)..
afterwards, if you want to get rid of the vamprism altogether, talk to an inn keeper after reverting to stage 1, he should direct you to a quest to cure it
An NPC is a Non-Player Character. Every humanoid actor in the game who isn't you.
Hi Wineguru - you contracted vampirism while fighting vampires. There's something like a 10% chance that you get it. Once infected, you'll see some warnings while you play. For example, when the sun comes up, the screen will become hazy and red for a few seconds. There'll be a message saying something like 'You feel a strange weakness as the sun rises'.
You can check the Active Effects menu - all diseases are listed in red. You can cure yourself of any disease by drinking a potion of Cure Disease, by getting blessings from a Vigilant of Stendarr (who are usually wandering around the world so kind of hard to find) or by praying at any shrine. For example, there's that preacher in Whiterun, up by the palace, next to that big tree, and he's standing in front of shrine of Talos. Just go up to the Shrine until you see the 'Activate' option. Do it and you're cured. The cure for stage 4 vampirism is more involved, but all the earlier stages can be cured at a shrine
Good luck!