Why did i gain two and a half pounds?

Okay, so this week actually I started trying to lose weight again. I went from 139 to 135.5 very quickly... WEll... yesterday... the only things that i had that weren't normal for my diet was a double chocolate chip frappucino from Starbucks and for dinner I had spaghetti and meat... I think I got too big a platebecause i was stuffed... I had that around 6:30... Well when i woke up it said i was 138!!! I'm really sad ... and yes i weighed myself right after i went to the bathroom first thing in the morning... No, im not about to start my period... What i want to know is... is this permanent? Will it go away tomorrow? Or will i have to spend four days losing it? =(