That you get attacked may be caused by a bounty, as they should only attack a stage 4 vampire.
Feeding brings you back to a stage one.
Approach a small town or farmhouse at night and its easy to break in and feed undetected.
Innkeepers should direct you to Fallion.
If they do not that must be a bug.
You can try to join the companions.
Spoiler when you become a werewolf, your vampirism is cured