Legal Question in Real Estate Law in California

As I understand the sequence of events, you were a single person at the time you took out a 2nd mortgage jointly with someone who was, at the time, (a) legally unrelated to you, and (b) had been previously decreed to be the sole owner of the mortgaged property. Then, you refer to it as "our" home. In what sense was it "our" home at the time the 2nd was taken out? Maybe you had some legal interest, some right, or maybe just an emotional attachment to it, but that isn't clear to me.

Was the 2nd mortgage necessary to carry out some part of the judge's order, or were you voluntarily trying to help your ex, or perhaps trying to prevent foreclosure on a home where you'd been awarded continued rights of occupancy?

When you agreed to become a co-borrower, (a) did the lender know about the judge's ruling and the ownership situation? and (b) did you have any sort of agreement, hopefully written, with you ex regarding your participating with him as a co-borrower (or guarantor or whatever)? I think as far as any equitable interest in the home, you're out of luck, but if there were any fraud or other unusual facts, maybe you have a case.