That is so wrong! I'm sorry he snuck around behind your back like that and wasn't even going to tell you about your own child... the child he would not be able to have baptized if it weren't for you!
A few times I suspected my ex would do the same thing; he's Catholic (though a barely practicing one) and I am not. I would be pretty ticked.
But as you do go through the legal system, be SURE you mention this. I have physical custody, and share legal custody with my ex, which theoretically means we both have input on educational, health and religious stuff. So considering your ex does not have primary custody nor primary decision-making, he didn't even have the right to do that. A very good reason to go for full physical AND full legal custody of your child - you can point out that look, he didn't even include you in a major decisions about your child. So I hope his action bites him in the butt big-time, ultimately.
Plus, when you do find the church, I would let them know their policies to do that without the mother's consent was really uncool. (I know nothing about Catholic rules, but I know they do annull marriages sometimes... can they annull baptisms

if it turns out both parents did not give consent?)
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