The first question you must answer is whether you were lawfully wed in the first place. If you were, whether it was by common law or with a license and ceremony, your marriage must be ended by divorce.

Only a few states recognize common law marriage. See Common Law Marriage FAQ for a list. Even in those states, merely living together does not mean you are married. You must intend to be married and hold yourselves out as such in public. Jointly registering your marriage with a county agency would likely be enough to allow a court to find the necessary intent -- and in that case, you need a legal divorce before you can marry again. The fact that your ex registered another common law marriage probably makes his second registration invalid, not his first (with you). You probably want to check with a lawyer who knows the law in your state to get this all sorted out.