I don't have any real advice but wanted to send you lots of hugs I have a 4 year old and he still we're nappies at night aswell and while he isn't doing poos in his undies he has started smearing poo all over the toilet walls evrytime he goes. Maybe it's a developmental thing to have a bit of a relapse.....not sure though?? Hopefully it passes soon I would just continue being consistent with the praise etc.sorry im not more help