Well, that's an interesting question. For many, an eating disorder is a way to create control in an otherwise out of control existence. Perhaps not the sole reason, but "wanting control" is a definite personality trait of many, many, many people. And the ironic thing, is that the eating disorder always gets out of control. We can't stop on our own.

The shame you are putting on yourself is only going to make you feel worse and more susceptible to relapse. OK, you messed up. You said you don't want to tell your step mom because you "only" lasted two days. Well, two days is a start, isn't it? If you go from binging and purging 20 times a day to once in two days, isn't that a good sign? Not perfect, of course, but better than it was before?

I'm in the same situation as you. I'm really trying to stop binging and purging. I slip up once in a while. Maybe my approach isn't even the best. I try not to blame myself when I relapse. I honestly expect it to happen. If I can go two days without binging and purging before a relapse--well, maybe next time I can go four days, then six days, then eight... you get the picture. The relapses will become less and less frequent and the impulse to binge and purge will become weaker and weaker. That's what I'm aiming for, anyway. It's not perfect, but it's better than nothing. It's better to relapse and start over than to give up, right?

If your step mom is supportive, I would definitely take advantage of that. "Mom, I messed up after two days, but I want you to know that I'm going to keep trying."

It's tough. I also struggle. Hang in there. Keep us updated.