No you're not doing it wrong if you're having 3 packs a day plus water and not doing too much exercise. Our bodies just dont lose at a consistent rate. Also in your first few days your body will be shedding water and glycogen stores, only once those are depleted will it start burning fat which goes a bit slower. As for it going up slightly, that's normal, our bodies will weigh different amounts at different times of the day and different days of the week. I have at least 2 days a week where my scales dont move and at least 1 day a week where the weight goes up, even if I've been 100%. That's why they only recommend weighing once a week, although I still ignore that and weigh daily.