My DD1 is doing this too. She is 2y7mo, and has been accident free since at least 2 (? even earlier - we had been doing EC).
I have been trying to suggest that it's toilet time, rather than ask her, because the answer is always no, but still she is absolutely refusing to wee! She will stand there, holding her fanny, and hopping from foot to foot, and still says she doesn't need to go, only to have an accident. She has been having accidents quite a bit over the last 2 months or so, whereas prior to that we had been fine. ??????????????????