ive been turned itno a vampire and fallion wants to kill me he tells me i double crossed him cant recall..dont want to be a vampire cant finish quests. some how i got off track and need HELP thanks

Escape Falion and feed on a sleeping person -- this will cause him to stop attacking you, hopefully, and you can hurry up and cure yourself before the condition worsens again. Other possible causes for attack might include harming someone close to him (his sister, the Morthal innkeeper, his young ward, or Lami, the owner of the alchemy shop), stealing from him and letting him catch you, or having a bounty.

If you have further trouble, do tell.

Oh, and you say he tells you that you double-crossed him -- I think you might have misheard something; he can potentially say "No one crosses me!" while fighting, but this is just decoration, and you didn't really "cross" him, or so I hope.