Right well 20 pounds in a month is really a lot. So that suggests you are having a famine reaction. According to Dr Amanda Sainsbury-Salis from the don't get fat diet, you need to eat more now.
Don't worry the that you will put on all the weigh thou lost just as fast. You won't if you stick to eating healthy whole foods.
What has happened is that you've triggered a famine reaction which is that you've lost too much fat and stopped producing so much leptin. This triggers your appetite. Its the body's way of trying to save your life, because it doesn't know you are on a diet. It thinks you are starving to death. I'm not going to try to explain it in any detail. Just read up on the resources i've already mentioned.
But eating more is what you have to do now. Eat lots of fruit and veg at appropriate meals times. Eat decent meals. Eat protein, and i would say some carbs, good fats, dairy. Eat unprocessed foods as much as possible.
What i have found really clear just in the last few weeks is that if you eat in courses, smallish sized of each thing its easier to assess when you have had enough to eat with out overeating.
So if for breakfast you have say a fried egg on toast, plus some fruit, you can see if you need to eat more straight away. Then you could have some yoghurt and cereal (not sweet stuff preferably).
For lunch, you could have an open sandwich with lots of salad vegies or a big salad with no bread but instead maybe some thing else that would fill you up. But keep up the veggie bulk. Again if after that you are still hungry, have some fruit or a piece of cheese perhaps.
For dinner, try to start with some vegetable soup, or lentil soup or something like that. And then your meat and veg or whatever you do. Tehn if you are still hungry you can have some more fruit.
I find i do not need to spend a lot of time cooking actually. When i make most of my dishes, like a soup, i do it once and i've got enough for a number of serves. Unless i'm making something like fried rice or pasta many things i make will last for several meals.
Other things, sardine sandwiches on wholegrain. Bean and veg salad with nuts and cheese. baked fish and veg. omelette or frittata a. bla bla.
I have only recently started doing the courses and i find its great. Its the french way.
So get to eating. I can tell you this works because its just what i have done for the last month. I increased what i have eaten and i have not put on any weight at all. Now i have started to think about reducing again. I don't reduce drastically. And i plan to take my time. I've given myself till the end of the year. Last night i waas thinking i might even take a month break every month. the idea is to keep my hormones and metabolism in perfect balance. If you read all those things you will understand where i'm coming from.