Everyone is right, you've had great losses, especially after losing 6 stone!!
Some people do see big losses on their first weigh in, but they are usually people who haven't lost any weight previously at all, and have 100% completely changed their diet, and often the people who have a lot of weight that they want to lose.
My first loss was 2.5lbs also, but I already ate quite a bit of fruit and veg, it was just other foods that I was eating that were the problem! As you (I assume) were already eating relatively healthily (you must have to have lost 6 stone!
) your body will be used to the healthier foods.
Ali has great tips though, try changing your foods around frequently, don't eat the same things over and over, your body gets bored and stops working hard to process what you are eating. And don't stop using your syns, they help with losses. Make sure you drink 2 litres of water each day, not counting fizzy drinks and tea/coffee (apparently tea/coffee dehydrate you slightly). Also don't over eat on fruit. As much as SW say it's unlimited, because there is sugar in fruit, eating too much can hinder your losses. I've noticed in the past when I've reduced my fruit intake, but kept everything else up (veg, meats, etc) my losses got a little better. Pasta, rice, potatoes should also be in measured portions, don't have more than 1/3 of your plate filled with those.
Do you have much more that you want to lose? If you are getting closer to your target weight, it could be your body starting to slow down. That does generally happen when someone has lost most of the weight that you want to lose.