This is truly awful to be going through your experience. But you wrote that you do not sleep. There is research showing that not sleeping will make you put on weight, other things being equal. So the first thing to take care of is getting enough sleep every day. Will help with the mental condition as well. Do you have any medication for sleep, is there anything, like a warm bath at night, that can help you fall asleep, is Melatonin - a pill or two - any helpful? Do you swim? I know nothing about knee replacements, but just from elementary physics I would think that swimming would be awesome for you - simple gentle swimming, not going to the Olympics.

You fear gaining weight==>you need to sleep, not purge. I can understand giving in to purging, but cannot you throw away all the laxatives or give them to your doctor to keep? I recently gave my Zyprexa to my doctor because I had extras and I have a history of drug overdose suicide attempt. Why risk it? Just get rid of the stuff. And congratulate yourself - you are so much closer to your goal than you are to your old you. As you know, it is marginally more difficult to shed each successive pound. This is going to be difficult. Give yourself time. It is OK to stay at your present weight for some time, because it is more important now to start going to the bathroom normally than to be at any particular point on the scale. Keep only enough laxatives for emergencies and give the rest to the doctor.