The only way you don't lose weight is if you eat calories equal to or greater than what your body needs. I have the feeling that you eat far more than you realize. You might mindlessly eat and forget about it. I've seen it many, many times.
Or, in response to some emotional loop, you'll binge ridiculously and write it off the next day completely forgetting about it. The thing is, your body doesn't forget it.
Eating 3500 calories per day and not letting yourself go above that for any reason should be doable for you.
We can optimize the diet to better satiate you too.
For instance, protein and fiber are both nutrients that have been shown to satiate better than others. Right now your diet is almost void of them, so no wonder you gorge. You need to clean the cupboards of all your 'trigger' foods that you tend to overindulge in.
Processed crap is easy, but it's also low in nutrient density and high and calorie density. It's also not filling and often times this is a matter of addiction I believe. Once you start, it's hard to stop.
Abstinence. Get used to it.
If you feel the need to gorge, replace those crap options with high nutrient density, low calorie foods like fibrous veggies. These things you can eat almost limitless amounts of and not worry about going over your caloric needs.
Before you start worrying about this stuff though, you need to right your mind.
Keep us posted