Hiya, my first thought is, are you eating enough? If you eat too little your body goes into starvation and slows down your weight loss. Try upping your syns for a week and see what happens.
The other thing (that's my personal downfall) is watching my portion sizes on pasta and rice, as I love them! so I keep an eye on those now.
Are you drinking enough water? You'll probably find the people who had a big loss in the first week drank loads, a lot of that initial weight loss will be water; if you drink more, your body stops retaining so much.
Lastly...you are 3lbs down and I know it's absolutely gutting when others seem to lose so fast, and it seems not a lot of loss for quite a lot of trying (I've been there!) but 3lbs is 3lbs! I only lost a 1lb last week and was quite disappointed, and a lovely lady on here told me to go and google what a pound of fat looks like. After seeing that, I was just pleased it was gone from my body!
You will get there, just stick at it hun. Different people lose at different rates, think of it this way though, if you consistently lose 1.5lbs a week for 6 months, that's almost 3 stone! Which would take you to your target, looking at your stats. Its not a lot of time in the grand scheme of things
