Hang in there hun. I don't think the question you need to try and answer is how do you stop these thoughts, but rather, how do you push them aside (and eventually push them out of your head) and replace them with good thoughts and affirmations. When you were in Renfew, did they give you any advice? What if you tried to write down your bad thought and phyically cross out that thought on the paper....rip that thought up and throw it out...and then, think of 2 good things (positive things) that you can write down on an on-going list that can help view yourself in a positive light. Even if you don't believe them at first. That's okay. It's kinda like admitting you have negative thoughts and realizing that it's okay...but that you can replace them with positive affirmations. You know how much a smile can make a difference in changing your mood when you are feeling down. They say that simple things like smiling and laughing can have a positive impact on mood. What if you tried the writing down the bad thoughts, ripping them up, and starting on a "good thoughts" list. Just a thought.
You've done really great eating and doing better - please don't let that slip.