Sorry I have to say this, but you cant be sticking to the plan. You need to be honest with yourself with your diary.... it means you write down EVERYTHING you eat, that very little bit hear and there. Also you need to weigh ALL your food that requires it, guessing is not enough. You need to drink in excess of 2lts of water per day.
I started the plan in March and have lost over 4 stone with a constant loss rate, I stick 100% to the plan. I write down everything I eat every day.
There is a story that goes around about a SW member who said the same as what you are saying, she wrote to SW HQ complaining about her yoyo loss. When she actually got courage to look long and hard of what she actually ate she wrote down everything that passed her lips each day. The result was that her syns were in excess of 55 and 70 per day. Her diary said 12 to 15 per day !!!! she nibbled bits hear and there, pinched of her kids plate at meal prep time, she guess weighed her food etc.
Believe me the plan does work but you need to stick to it and be honest with yourself, the average loss is between 1 and 2 lb loss per week. In saying you started in July your loss should have been around the stone mark and thats without the gym.
I am sorry to be direct , but I'm sure you know deep down the reasons for poor loss. But please don't be dishartened with what I say as we are here to support you and get you back on a winning path.
Good luck and give it another go.!!
Phil x