I just posted something about starting a fast in my latest post on my blog. Fasting is a really big undertaking and if it hasn't clicked in your brain that this is what you are going to do, no matter what happens, you are just going to go on autopilot and at least try it out for a week or however long you are planning to fast, it's pretty much futile to try. If you have not committed wholeheartedly with your mind and your body to the idea, it will break you down and make you eat a lot, which really only makes things worse, as I'm sure you are not feeling good right now. So, my advice is that if it has not yet clicked for you, try to maintain a diet that will at least allow you to lose weight slowly, whether that means for you that you just watch your calories, limit your intake of certain foods, eat low carb, eat low fat... whatever it is that works for you. That way you can at least make some slow progress while in the back of your mind, you get ready for the fast. You will know when you are ready. I had tried to fast in January and February of this month, but it only ended up in my overindulging after just a day or two of trying to fast. Then, I tried to just stick with a low calorie, then later with a low carb diet to at least slowly lose weight.
Finally, in September it clicked for me: I was exercising daily, I was eating low carb and had tried all kinds of variations on that, had cut out the dairy, had cut down on the calories I ate on that diet, and I still was not making visible progress on my weight loss. It clicked because I was just tired of it: I have been unhappy with my weight for about five years now. It's great that I have overcome my eating disorder and that I am able to maintain a weight range, but I hate being just a little pudgy all the time, hate not wanting to have my picture taken, hate not being able to wear the clothes I want to wear, hate that I would always rather stay in than go out, hate that I don't like to see my reflection in the mirror. I just hate all those things, and it doesn't have to be that way. That's when I committed to the fast, and it was just clear to me from there on that that was what I had to do. I told myself at the beginning that I was just going to have to go on autopilot, that it would take quite a bit of time (i.e. this is not a 7 day fast thing), but that I know that I can lose weight on a fast, while apparently low carbing with an approximately weekly cheat is just not good enough.
If you want to talk more, feel free to email. I'm happy to give you whatever support I can give.