I think that's Come What Come May (Time And The Hour Runs Through The Roughest Day (http://theshyauthor.livejournal.com/2285.html)) by theshyauthor.
"Jensen, a student at the University of Washington and grumpy person in general, is not at all impressed by the fact that Jared Padalecki, son of a famous country singer and a popular Hollywood actor and general heartthrob of the nation, also decides to study at the same university. He's also not happy about the fact that he ends up at Jared's house party thanks to his best friend Danneel, but the morning after a panic attack, when he wakes up in a strangers bed, he realizes that Jared Padalecki maybe isn't as bad of a human being as the magazines make him out to be."

That's it! Thank you so much.

I was looking for this recently, too, so I'm so glad you requested it!