Help!!! Self sabotage

Hi everyone I hope you can help me.
I'm currently having therapy for my low self-esteem issues and part of my problem is my weight. I seem to use food as a protection mechanism, deliberately eating more to hide myself from the world. I want to lose weight, but as soon as people start complimenting me on my thinner appearance or the scale gives me a number I approve of, I go and deliberately ruin it. It's almost a sub conscious action. I don't think to myself "I need to ruin this now" and grab a cake. I just eat like mad!
I also eat excessively when I feel under stress, or vulnerable.

Does anyone here have any advice about how to break this awful cycle? I have a wonderful holiday coming in a couple of months and I worry that all my good work in therapy will be undone by some horrendous holiday pictures of me spilling out of my bikini.

Please help!!