Divorce as a new convert

Ok, I’m in a bit of a pickle, to put it lightly. My husband disclosed to me a couple months ago that he’s been having an affair for six months and more importantly, that he wants to be with her, aka leave me, aka leave our family with two young kids. I’m a stay at home, homeschooling mom and spent the past four years significantly disabled by a condition similar to MS. My health has gotten better in recent month but I’m still not yet able to work. He says he wants to support us as much as possible and have us continue living the lives we are (paying for the house and car, the kids’ activities, me staying home and homeschooling), but he’s leaving the marriage and family for this affair partner.

Obviously I am heartbroken for myself and the kids most of all, but I am also scared. I am a new Catholic convert and was just baptized and confirmed not long before my husband dropped this all on me. He was not and is not catholic, though he was baptized as baby. Our wedding was not Catholic but was recognized as valid.

I don’t want a divorce, at all - I was committed for life - but it’s not my choice, and I need to protect myself and the kids legally and financially. Advice from divorced friends and r/Divorce has all been “get a lawyer now” and “you need to file first and file fast”. But my understanding from speaking with my priest is that I cannot seek divorce, though if he does and I have no option I am not at fault. Thing is, he’s not going to. He wants to have his cake and eat it too. I’m the one (me and the kids) who’s put in danger by not acting on it legally, so I feel like I’m getting trapped between a rock and a hard place. I’m not sure if anyone’s been through anything similar but I am in desperate need of advice. Thanks in advance.

TLDR: being told I need to seek divorce to protect myself and the kids legally and financially but as a new Catholic have been advised that I cannot seek divorce.