sometimes you will sts, this happens with everyone occasionally, it shouldn't make a difference how much you have to lose. The Slimming World diet WORKS!!.
All I can suggest is to take you weekly meal planner to your meeting, so that it can be looked at by your consultant incase there is something you are doing slightly off plan.
I expect you will not need to though, one week of STS does not mean it will be the case every week. You did very well to lose 5lbs already.