I couldn't help but notice your screen name and relate it to these two posts. I don't know you or your situation and only want to help with positive intentions. Is it possible that you suffer from depression during your "down" cycle and during that time, extreme weight loss seems to be the answer to your extreme-feeling down cycle? And when you are moving towards the "up" cycle, you feel better and therefore have less of an attraction to your extreme weight loss goals as the problem seems somehow "solved" when you feel better? If you have untreated bipolar disorder, find help for that and I bet it will help you in a lot of ways. I am guessing that your eating is inconsistent in line with your mood changes - extreme restriction during depression and very liberal intake during happy times. That inconsistency might be causing you to be unhappy with your weight. If you can receive treatment for your bipolar disorder and find a way to eat more consistently, I think it will swing backwards and help your mood changes also because (I am still guessing) that when you are in your "down" cycle, you regret the liberal food intake from when you were "up." As with everything else, food is itself not a problem and changing food is not the answer. There's an underlying problem that you need to address in therapy that will come out and roar as you work through it and separate the feeling that this issue causes from food. We label "anxious, insecure, sad, rejected, depressed" as "fat." It's an easier label to deal with because it has a solution - diet. Dig deeper and get help.
And post here as often as you want! Check out the Depression and Weight Issues forum. You will find a lot of support there, also.