Secret son

Hi moms. I need support or some advice I’m so confused... a few days ago my husband received a form from work that they will automatically taking money out of his checks for child support. They will be taking 50 percent of his income. The thing is he’s never known about this baby. The mom never told him she was pregnant. I don’t know what to do. We want a DNA test for sure but don’t know how to start that process and he’s it’s his obviously going to pay support. we have 3 kids. I’ve been dealing with really bad postpartum anxiety and I don’t want to deal with this or want my kids to deal with this as well. I know it sounds so selfish but what would you do in my situation stick it out with husband and then deal with baby mama drama that I never signed up for. And please be honest. This has been super stressful for me he seems like he doesn’t care or want to deal with at all. I’m the one calling the courts, filling out paperwork and taking care of my kids and home. While doing all the paperwork and stuff I just start getting SUPER INSECURE about his past. I understand that this baby was someone was from the pst and I understand he just found out as well but for me mentally it’s not ok. I feel SUPER resentful. What would you do in my shoes..

EDIT : WE ARE IN CALI.

We never received any other forms

All we received was a income withholding form. We have to file a income and expense form

If we want DNA we have to summit an order which is 465 OOP

Child support told us they don’t handle it the court does.