Hi C's Mom,
Not that is going to help you much right now, but there will be days that you feel better about all of this.
My daughter has been suffering from this her whole life and she is now 8. Checking her body has become second nature to me, I am able to predict how she will do on any given day, but strangely enough I am not able to prevent anything from happening: it is not my problem, it is hers. Giving the problem to her has been the hardest things I had to do. Also, you need to learn to realize that the problem is the problem, not your daughter. That all said, I found myself yelling at my kid again today, because she had an accident in school and put her dirty undies in her backpack without a plastic bag (lovely smelly backpack!).
I found (and still find) that this problem eats away on your confidence as a mother. My reasoning goes something like "if I was a halfway decent mom, I would be able to solve this problem". It deosn't help that most people I meet have no way of understanding what she goes through every day (but if she needs to go, she could go, right??? No, wrong, she doesn't feel her poop, she doesn't smell her accidents etc etc...
Right now Anna and I are in a good place. After years and years of trial and error I have decided to finally follow my gut feeling. I halved her dosage of Miralax (the pediatriac gi said that soiling had something to do with impaction, I believed it was just too much Miralax) and I have become extrmely strict with bathroom routines. It helps, we have a lot less accidents. But anything throws us for a loop: birth day party, getting up later in the weekends, one forgotten sits, not enought too drink, or all of a sudden too much to drink...
The frustrations are sometimes overwhelming!
By the way, there is a specific message board just for this problem. I am not sure I am allowed to mention it hear but look under aboutencopresis.com.
Good luck C's mom!