As far as a developmental regression, not that I know of. She has never had an accident when she's been at school, but that could be because they do bathroom
visits often. School seemed to reforce the potty training. Maybe being on summer break affected it? She isn't under any stress. I am, but I don't show it. One thing I have noticed after she saw a friend breast feeding her baby a few months back, is that she tries to act like she wants to breastfeed and says she is a baby since then. She stopped nursing at age 2. I tell her that she is a big girl now and that she needs to go pee pee and poo poo in the potty, not in her pants. She just looks at me. She has a sweet temperament.