Busybee, rather than feeling despondent, be proud that you've lost 3lb and your journey has started in the right direction.
Weight can vary throughout the day by more than you think, this is why your Consultant will recommend that you weigh in at group every week, at the same time, and wearing the same sort of clothes. And don't be tempted to weigh yourself throughout the week, that's a bad habit to get into. Simple things like toilet trips, big pasta meals the night before, retained water (the ladies have better reasons for this than the men do!) all add weight,
but not fat. Also, and I'm not sure if this is actually true but it seems to be the case in our group, if you've done a shedload of exercise it tends not to show up until the following weigh-in. I've read about water retention to repair muscle after exercise, but again I don't know if it's true or an "old wives tale". On weeks I've done lots of walking I've posted 0.5lb or 1lb losses, then the next week it's been 4.5lb+ even with some extra wine thrown in. Moral of the story (if any) is chill out and keep going.
In the long-term it will show, and your instincts about feeling lighter are probably correct - just keep to plan and focus on your long-term goals, not the short-term weigh-in data. Good luck!