You are correct that the procedure was objectively wrong, because the intent appears to be to prevent pregnancy because of your wife’s medical condition. As you now know, that is not an acceptable course of action. However, at the time, you did not understand the seriousness of your action, so, even though the first criterion for mortal sin was present, grave matter, you apparently did not have full knowledge and consent, which are also necessary to make your action mortally sinful.
With all that understood, I am quite sure you are distressed by your actions and would like assurance of the Lord’s forgiveness. You may bring this up in Confession and receive absolution, regardless of the actual seriousness of your sin. The Church does not require people to reverse their sterilizations in order to be forgiven, so do not worry about being asked to do that.
So you would simply say in Confession what you have said here, and everything should be just fine after that. Then, as Island Oak suggested, live your lives in gratitude for your two children and your wife’s health.
God bless you!
Betsy
