I've told him that I hate it and normally say something like 'Don't call me that, I have a name' but he ignores it.
He also kind of shouts it in a really grating way ie. 'Here you go Mummy' while playing with my kids and throwing a dirty paper towel at me to throw away, for example.
It makes me feel like I'm not being seen as a person, and honestly makes me feel a bit sick to be called that by someone who's not my child. AIBU?