[ Diet & Fitness ] Open Question : Why did I gain 6 kilos when I was only trying to lose 5?

I was 70kg, fairly happy with my body, but decided to get down to 65 for sport competitive reasons. I've been visiting the gym 3x a week doing a whole body workout and running for 20 min 3x a week too. I haven't done much sport training due to a hell of a lot of stress at work and getting no break between work and sport. How could I have gained 6kg instead when I've been fairly good with what I've been eating (although I don't calorie count - I hate it when my free time is spent calorie counting), but do find that when I'm stressed, chocolate seems to find it's way to my mouth. Now I have twice the amount of work needed to do, and I'm getting so fed up and depressed over it. Items of clothing that used to look good on me now look feral - like a fat chick trying to fit into skinny clothing :( How can I refind the motivation too when I got such bad results????