4 yo DD soiling pants after months of being clean, what's going on?

[soupmaker]

Here we go again. DD started toilet training over a year ago at nearly 3. It's been a bloody nightmare for 12 months. She's never been reliably dry, although now has more dry days in the week than wet. She is also still very wet at night. Over the couple of weeks however we are now getting soiling on a regular basis. She cracked poos after three/four months of training, so what's this all about? She always holds on until the very last minute, often declaring that the poo is sticking out before getting to the toilet. She's pretty regular, most poos appear an hour or so after getting up in the morning. Its driving me demented. I thought we were at last getting somewhere. I'm at my wits end, yet, again. Is this normal? Its not usually the whole poo, just a bit of poo as she has waited to long before going to the toilet, or in other cases seems to be a wee bit of poo and then she manages not to do a poo. Does she have some sort of cast iron buttocks, holding them in? Oh, how I long for this all to be over and to be able to leave the house without a bag full of pants.