Hey adaem,
You're not a failure
. You're just human- believe me this has (or will) happen to almost all of us (and more than once). Some days or weeks go great, some are hard. Sometimes we find ourselves undermining our own progress.
I know from my own experience that sometimes that kind of eating (especially after doing so well) is emotionally driven. For me it can be anxiety about taking care of my health, body, self. Sometimes, when I've been staying with the program really well, something in me gets really anxious. Perhaps it's fear of failure and to deal with the fear, I eat to keep it down. Or sometimes I wonder if it's me trying to make the failure happen sonner, that on some level I must think is inevitable, so I can get past it.
The things that help- trying to get to the root of the un-hungry eating. Writing in a journal, talking it out, coming to this forum. Being conscious while eating. And, yes, sometimes being DELIBERATELY unconscious while eating. Be kind to yourself. You are not a bad person and not a failure, you're re-learning your relationship with food.
Figure out if you are hungry (need food), have some emotion you're trying to avoid, are tired, feeling deprived, etc. There are so many reasons for each of us and it isn't always the same.
Take it as a learning, start again. (Sometimes I have to start again several times in a day.) You did a brave thing coming to this forum. There are lots of folks here to help. And good work on the walking.