I wonder if you are eating enough of the right things even when you are on track.
"Plateauing" is a common problem if you have restricted your calories for too long because your metabolism will seize up.
Are you following a particular plan? I wonder if what you are eating has ceased to work correctly with your body and so you are yo-yoing and craving crap like this.
The sort of programme you need to follow to start to lose weight is often not appropriate for later on when the amount you have to lose is less. Your body is behaving differnently now because, let's face it, there's 4 stone less of you.
People think the answer is to eat less. In almost all cases the opposite applies, especially if you are following an exercise programme as well because you now have a muscle mass which needs feeding differently.
First thing to do is to forget what has happened today. Do not beat yourself up.
Go and stand in front of a mirror and shout at yourself for being bloody spectacular for losing 4 stone. Start praising yourself for your good points. If you have good teeth - go and have a good look at them. If you have nice nails - go and examine them. Start writing down all your wonderful qualities ie what you do for your children, for charity, presents you have bought that have made people really happy, the time you spend with elderly relatives etc.... etc ....
Get into a head space where you know you are the dogs doodahs.
Get yourself something high in protein and eat it slowly. Drink plenty of plain water. Get some exercise (it helps to balance your entire body patterns).
Get busy. Do something you weren't planning to get done and praise yourself for it.
Grrrrrrrr. (Maybe it's just me, but I have to get stern with myself.)