Why can't I stop shoving crap in my mouth

Food obsession comes from deep within, being overweight is more than just being lazy, often there are psychological issues that need to be faced. "Filling a void". Like @GWehsling said, I think a step is seeing someone, even if its just to talk. As for why you can't stop... only you can answer that, but we are all here for you, and Im hear if you need a pair of ears.

It can be a psychological thing, like the above posters said, such as compulsive eating disorder, or binge eating disorder or emotional eating:
http://www.helpguide.org/articles/diet-weight-loss/emotional-eating.htm
http://www.helpguide.org/articles/eating-disorders/binge-eating-disorder.htm

But it can also be a physiological thing too - are you eating enough calories (generally?).
If we're starving hungry, we tend to make bad choices, like eating the whole pack of cookies in one go, or heaping on a double serving.

It can be a mix of the two as well. I tend to suffer from disordered eating myself, but it's a heck of a lot easier to make good choices if I'm keeping above 1400 to 1500 calories a day.

What could help you, at least it helped me, is noting down how you feel sometimes after eating crappy. I used to mercilessly overeat with for example buttered nutella bread. I felt awful after it. In general bad eating habits often caused me stomach pain, but also the overweight used to make me feel bad. And sometimes I wrote down, as message to myself, how I felt in that moment. That it is not worth it. That I wish I had not eaten that. That eating it wasn't much fun, and I don't feel better. Reading this sometimes helped remembering not to do it. Reading how unhappy I actually was with those choices.

I also did it with exercising. Noting down how great I felt after it as encouragement for when I feel demotivated.

Also I agree with the other posters here, you need to address the reasons of why you do this. I tended to do it to feel safe. I avoided my studies and tasks and used food to make a day "bad", so I could just stay at home, eat and play games all day. Often without bad conscience, you know, because "tomorrow" was gonna be better It's just fooling yourself if you do this, because days become weeks, weeks become months, and then you have lost another year without really being happy.

Another method is sneaking in healthier stuff. Maybe forget the radical change, like "tomorrow I will replace all the carbs and the sweets with vegetables, fruits and yucky green smoothies". Ofc you will back away each time. For me it only worked when I stopped categorizing days into "good" and "bad", and allowed myself to have for example a salad for lunch, even when I had chocolate for breakfast. Usually I would have gone "the day is f*cked anyway, use the opportunity, eat the spaghettis, eat them all!!", even if I actually wanted to have a salad.

Combine mixing in healthier foods with exercise. Exercise first, then go grocery shopping and see what you want then. Maybe you will want to make healthier choices.

If it fits your macros/calories, you can still eat chocolate and cookies and get results so don't beat yourself up over it.