Why am I going the Other Way?

So, my body has now decided to move the other direction which is so frustrating and I have nothing to blame it on like cycles etc.  I have still eaten well and exercised over the weekend, but I have gained like 2 pounds, grrr.  I was so frustrated with it last night that when I went to Sunday dinner and my sister-in-law made my favorite dessert (that she makes anyway), I ate it.  It was homemade key lime pie and I usually think it is too sour but she makes it so yummy.  Anyway, I ate 2 pieces (was only going to have one but then my son didn't like his and gave me the rest).  Going to try really hard to not only avoid sugar this week, but eat really healthy and exercise every day!  Really hoping for a weight loss by Friday, we'll see.  Boo.