I was born a Muslim. However, I have never practiced Islam and had no one to teach me the fundamentals of the faith. I am now married to a non-Muslim man and have three children. What is the opinion of Islamic law concerning my situation? What should I do now that I know that a Muslim woman is not allowed to marry a non-Muslim man?

Ibn ‘Abbas (may God be pleased with him) narrated that the Prophet (peace and blessings be upon him) said, “Verily, God has forgiven my community for their [unintentional] mistakes, their forgetfulness, and whatever they do under compulsion.” Based on this hadith, the inquirer is not blameworthy because she was ignorant of the fundamentals of Islamic law and committed an unintentional mistake. In addition, her children are legally attributed to her and her husband.

Muslim wives are prohibited to live with non-Muslim husbands
In Islam, Muslim women are explicitly prohibited from marrying non-Muslim men. Therefore, it is unlawful for the inquirer to engage in any form of physical intimacy with her non-Muslim husband based on the words of God Almighty, “They are not lawful [wives] for them, nor are they lawful [husbands] for them.”

The ruling
In order to maintain the family's stability which is one of the objectives of Islamic law, it is obligatory to inform the court (if you live in a country that provides this) that you are a Muslim, so that the judge will inform your husband and invite him to embrace Islam. You yourself may also invite your husband to Islam through kind advice and wisdom. If he complies and embraces Islam, then it is a great blessing and you must conduct a new marriage contract. Otherwise, separation becomes necessary based on the court decree.
And God Almighty knows best.