Most Beer is loaded with carbs (and calories). It also makes one have an "I don't give a crap, I'm gonna eat it" attitude. Usually with salty carby foods, (sweets don't go well with beer IMO). Chances are, you ate more than you think AND you are retaining water. Give it a week, and you'll undo the damage you did in 2 days. (Sucks doesn't it?)
If I were you, if you are going to drink on occasion, stick with clear liquor, (rum, vodka, gin, scotch etc.) They are mostly carb free and heck, if you drink enough, you'll pass out before 3 am breakfast...lol