Legal Question in Civil Litigation in California

Re: I signed my boyfriend as a second cardholder and he has me in debt for over 20k.

Of course you're stuck with the debt; it's your card. Good luck suing and collecting from him, because AMEX will have no trouble collecting from you or forcing you into bankruptcy.

Re: I signed my boyfriend as a second cardholder and he has me in debt for over 20k.

You are staying in a bad relationship because you're afraid he won't repay you? Get out. Pick up the pieces. Use an attorney and sue him (small claims only goes up to $7500 and it's harder for him to defend a regular lawsuit). If you win either he will declare bankruptcy, or you get to have fun making his life miserable until he pays in full, with interest. Keep good records.

Re: I signed my boyfriend as a second cardholder and he has me in debt for over 20k.

If it's your AMEX account, then you are "stuck" with the debt, whether or not you stay with him. The two things are not related.

If he is on the AMEX account, then he's jointly and severally liable. If he is not, then it's your responsibility.

If you have an agreement that your boyfriend will pay for any charges he makes, then if he refuses to pay, you can sue him for what he owes you.