His body, his choice.
However, the relationship between you is an emotional contract & the marriage between you is a legal contract. You are both equal partners in either of these relationships. It is reasonable to expect that if one of you considers/undertakes an action that directly impacts the expectations within the relationship &/or marriage between you that the other person is properly consulted beforehand & is no agreement or compromise can be found then the relationship &/or marriage has broken down.
For example, vasectomy, female sterilisation, moving abroad, leaving to live with another etc.
You have a stalemate here, neither of you is getting to grips with this & this is making you both miserable (& no doubt affecting your children).
Two paths, either
Make an appointment with marriage guidance to get help talking this over. This will take some time to get an appt & you cannot make him go.
Or see a family law specialist at a local solicitors & get advice about his action/alienation are grounds for a divorce. Get advice & facts. Make sure you know where you stand. As this is a very busy time for lawyers, you need to make an appointment for the advice soon.
He has done what he wanted to do.
The ball is now in your court.
I think he knew very well what he wanted to do & did so to provoke the end of your relationship/marriage.
Me, I’d make both appointments today, at the lawyer so that I am better informed & at the marriage guidance so that you both have impartial trained support for you both to understand WTF is going in between you, & you are both prepared either to stay together & rebuild or make a clean healthy break.
I’d say the same to your husband if you’d had an elective sterilisation without consideration between you, & circumstances were the same.