I'm looking for a fic that has Angel needing blood so he has to have someone give him some and Spike thinking Buffy is the one who voluntered runs to stop it and tries to tear down the door to get in but I think Anya or someone else tells him its Cordelia with Angel not Buffy in their with him.

Times Fool by MsJane has a scene like this, except it's in the future and so there's no Cordelia.
http://www.bloodshedverse.com/stories.php?go=chapters&no=12736

Forty years after the battle in Los Angeles, Spike comes in from the cold under the impression that Buffy and Angel are involved, which was why he stayed away. Angel keeps letting him think that, until Spike smells Slayer blood on Angel and gets upset enough to drop his blasé act.