I know divorce is wrong. I know adultery is wrong. I have committed adultery, got a divorce and I have remarried to a man that I had an affair with. He and I both go to church now and we both know we have sinned and have asked for forgiveness from God and our families. But now what? is it wrong to stay married? My ex-husband had committed adultery before also. What should we do? We are faithful members now of the church of Christ.
Notes like yours are difficult to answer, not because the Lord isn't clear about the matter, but because I know that no matter how carefully I word the matter, it isn't going to go over well.
Let's start with the basics, even though you know these things.
"But I say to you that whoever divorces his wife for any reason except sexual immorality causes her to commit adultery; and whoever marries a woman who is divorced commits adultery" (Matthew 5:32).
"And I say to you, whoever divorces his wife, except for sexual immorality, and marries another, commits adultery; and whoever marries her who is divorced commits adultery" (Matthew 19:9).
"So He said to them, "Whoever divorces his wife and marries another commits adultery against her. And if a woman divorces her husband and marries another, she commits adultery" (Mark 10:11-12).
"Whoever divorces his wife and marries another commits adultery; and whoever marries her who is divorced from her husband commits adultery" (Luke 16:18).
The fact that your ex-husband had committed adultery doesn't appear pertinent to this case since I take it that it had happened earlier and had been forgiven. Since you ended up marrying the man with whom you had your affair, I assume that the cause of your divorce, or at least a major contributing factor, was your affair.
Let's assume that the affair had nothing to do with the divorce. Then both Mark 10:11-12 and Luke 16:18 apply. Either of you marrying someone else commits adultery and whoever marries either of you is also guilty of adultery. Though you wanted out of your marriage covenant, God is still holding you responsible for the terms you willingly made in your first marriage. Covenants are serious matters. God did the joining, thus it is God who decides what allows the covenant to be set aside (Matthew 19:4-6).
If we assume that the marriage ended because of your adultery, then Matthew 5:32 and 19:9 apply. Since you violated the terms of your covenant, God still holds you to the covenant even though your first husband had divorced you. You will be guilty of adultery when you marry anyone else and whoever marries you will be guilty of adultery.
It is hard, but again, the matter of the marriage covenant is not something which was ever meant to be treated casually. "Walk prudently when you go to the house of God; and draw near to hear rather than to give the sacrifice of fools, for they do not know that they do evil. Do not be rash with your mouth, and let not your heart utter anything hastily before God. For God is in heaven, and you on earth; therefore let your words be few" (Ecclesiastes 5:1-2). The covenant you and your first husband made are binding for as long as both of you live. "For the woman who has a husband is bound by the law to her husband as long as he lives. But if the husband dies, she is released from the law of her husband. So then if, while her husband lives, she marries another man, she will be called an adulteress; but if her husband dies, she is free from that law, so that she is no adulteress, though she has married another man" (Romans 7:2-3).
Even in the case of one party in a marriage committing adultery, the covenant is not fully set aside. The innocent party is released by God to marry again if he or she chooses, but the guilty party is still bound by the original oath. I really wish people today understood that marriage is for life. Perhaps they would put more thought into who they marry and more effort in keeping a marriage functional.
So long as you remain with this man with whom you committed adultery, you both are remaining in adultery. You made a choice long ago to marry your first husband. It was by your choice that you destroyed that marriage. The consequence is that you live as a single person unless your first husband happens to precede you in death. Only at that time will you have the right to marry another.