I gained :(

For the first time in my dieting life, I have stuck to a diet, I haven't strayed at all, no chocolate, no fast food, I am eating fresh foods, drinking lots of water and I am exercising, I've started using my pilates core ball twice a day, I'm using my skipping rope, and I am walking a lot, and I've gained almost half a kilo. I don't believe I am gaining muscle because I haven't been exercising very long, so I am dumbfounded as to what I've done to gain weight. It's disappointing and I'm upset... but that DOESN'T mean I am going to go off my diet or stop exercising, I want to lose weight and be happy and healthy. I'm not going to go any further backwards.
Normally I would have given up and gone to macdonalds or hungry jacks and been miserable with a burger, but not this time. I had my sultana bran, skim milk and fruit for breakfast, salad for lunch and dinner will be my favourite salmon :)
Maybe next week I'll have a big loss