Kate, remember that a half pound down is far better than having put it on. I found in the early days of GL that I was being too generous with my portion sizes. For a couple of weeks then, I weighed everything to get a visual of the size of a portion. 25 or 30g of dry pasta is very very small!! In fact it was when I saw just how small the portions were on a GL regime that I started using more lentils, beans etc. These were more filling, more GL friendly and low in cals.
Keep a diary of what you eat and maybe then review it to see what else you might add or take away the next week.
I also drink plenty of water, at least three litres a day. It really helps keeping you feel full. Apparently 60% of the time we feel hungry it is actually water that our bodies are craving!
Keep strong. Remember a little down is far better than putting it on.