Context is everything. It depends what the op is. (As a pp said, is it a massive boil or growth being removed from your vulva? Or are you having your appendix or wisdom teeth out?) Although it is odd for him to discuss it over a WhatsApp group. So YANBU,
My DH is a bit of a gossip and can't keep his mouth shut and he loves a bit of drama, so I am careful with what I tell him. And I never tell him other peoples secrets or personal information, as I know he will blab. And he has been known to bleat my private information to people at work.
This one thing I didn't know about til one of them saw me in the street and mentioned it. One time (when I was in my late 20s,) I got very drunk after mixing my drinks, and was violently sick and really ill the next day. DH saw fit to share this with colleagues, and I was labelled a massive pisshead, a lush, and a drinken slob 'jokingly' when they saw me next, and they were asking where my drip was that was feeding the alcohol into my veins.
I hadn't drunk booze for about 4 months at the time, and had only had about 6 drinks, and as I said I mixed them, so was very ill. I don't know what DH said to them but you would have thought I was Oliver Reed or George Best!
I was really angry with him, and refused to drink when I was out with him for a year or more after that. And I also refused to go to any of his work dos, because the next one I went to after my vomming fit, his workmates took the piss all night. I could have killed him! So I do get where you're coming from @WHYohwhy12 Your partner has no business spilling personal and sensitive information to anyone, let alone his work colleagues!