hang in there babe -- i've done my time with ED, too, but gaining and losing and gaining when you're taking lots of pain meds has NOTHING to do with ED. Fear not. Frankly, I think you've moved beyond worrying about that old bear, don't you?
Personally, I decided that I might as well enjoy eating now! It's a miracle I even have an appetite some days, so when I feel the urge to eat anything, I chow down on the Yummy Treats! Pain and meds and everything do such a mean job on how your body is supposed to be working. Look at it this way: if you feel an urge to eat, that's a sign that the RSD has not affected your central nervous system! Yay!!!! Seriously - you can no longer use the tools you learned for thinking about ED in the same way anymore. Food means something different to your body. Psychologically it may still mean comfort, but I think that's OK, especially when there is so little that can comfort your body now. Also, there are some things that it is very important that you do eat now - maybe you could work those in? I'm fairly sure there is some good RSD nutrition guidance out there
hugs