I was naughty today but it tells me I didn't eat enough.

So, the thing is, when we are heavier, our bodies require more calories just to keep our organs functioning and get us through our daily movement. You can and should eat a fair amount more than the average person does on a weight loss diet. I started out at 256 lbs and could easily lose weight eating 2300 or even up to 3000 kcals per day (when I was active) when someone weighing 150 lbs might have difficulty losing at 1500 kcals/day. You need to eat enough food or else you are prone to losing muscle, binge eating, and other negative consequences. If you want to stay as low as you are, you must do it with a doctor who can monitor your health.