Evening, honey. I know EXACTLY how you're feeling. In fact, I was in tears last Saturday going through what sounds like the same thing. My particular problem was that I'd been kidding myself that I'd been staying on plan and writing off way too many pizzas.
Sarah has given you some great advice up above, so I can only really echo what she has said. I'll also say that for me, setting "mini goals" has really helped. At my old group they always asked us how much we wanted to lose the following week, which didn't really work for me, so I took to just setting myself interim milestones (you can see them in my signature).
If you're enjoying your group, then follow your consultant's advice and stay to group. Lay it all out when she gets to you in the losses roster and get them to rally around, because I bet you won't be the only one there who has ever felt like this.
Now for some tough love: stop beating yourself up for not being where you want to be yet. The only way you're going to get anywhere with this is to be patient and kind with yourself. The beauty of the SW plan is that is really is a plan to change your eating lifestyle, not a diet. Habits are habits because they're difficult to break, and nothing worth doing is ever easy. Keep going with this, and you'll get the hang of it. It might take minor adjustments, or it might take big sweeping changes. But you CAN do it.
And hey, if you ever start feeling down, take a look at this:
Always makes me feel better ^_^