A few things to consider:
Does she use it against you?
Does she blab about it to anyone else?
Do you tell your own parent(s) about the rows and what your DH has done?
Do you get on well with her?
If yes to the first 2, then YANBU because he should not give her ammunition, or allow her access to private info about you that she can use to fuel her own gossiping.
If yes to the next one then you're on a bit of a sticky wicket in terms of being hypocritical.
If yes to the last one but no to the first 2, then YA probably being a bit U.
However, your DH should realise that there are some things that his mother doesn't need to know. Does he tell her all about his sex life? No? Why, does she not need to know that maybe? Then your personal health issues should fall into that category too.
If 1 and/or 2 are the case, then he's an utter bellend for continuing to tell her anything about you. But if he still hasn't got that, then there's little hope he's going to now, unless you do the same to him and he realises how unpleasant it is.
If it's just that he can't deal with anything on his own without discussing it with mummy first then he needs to grow the fuck up and be an adult.
Realistically, there isn't much good about this situation though - but it might not be so bad if she's a nice person, doesn't blab or hold it against you and you get on well.