Hiya
I just mentioned this in another thread but quite early on in my journey, my consultant told me I was under eating and that's why I wasn't getting as big a loss I'd hoped some weeks. I took her advice and eat more (on plan) and used up all my syns. Despite feeling a bit guilty, and definitely heavier(!), I lost a big whack the following week, so I just continued like that. Now I know if I want a big loss in a week, I follow the plan 100% and use up all my syns and eat until I am full. It sounds like it shouldn't work but it does.
Generally in my group, the people who use their syns tend to lose more. I don't know if that's because it helps them stay on plan and makes them less likely to stray, but it does seem to work.
Do you go to group? It might be worth speaking to your consultant about it if it is frustrating you. However, 7lbs in 4 weeks is really good and IMO, sustainable. If you did that for the next 3 months, that a stone and a half off. And just the knowing that you are eating healthily is a good point, as ultimately that's better for you, even if it doesn't show on the scales.
Also, you might benefit more from doing measurements - waist, hips, legs, bust etc... as if you have taken up running/exercise you might fall into that slow weightloss category some people do at first. But seeing measurements decrease, is another motivator, especially if the scales are slower than you think they should be...