Was married before and have three children from that marriage. Unfortunately, it ended in divorce. I married my new husband in the USA in a civil ceremony. I became a Muslim after marrying almost immediately. We have never been married by Nikaah. My husband is from Egypt very close to his family and I respect all his wishes not to hurt them. He has never told them that he is married to me for 6 years now. I was told they would never accept me because I am not Arabic and have children from a previous marriage. (My former husband was also Arabic).
When we first got married, I told him it would be very difficult to get pregnant but not impossible. He told me at that time he did not care about children.
Now to my problem! As I have said before his family knows nothing of me. However, I just found out that he got married in his country this past summer and his new wife is now pregnant with their child. He never discussed this with me. I am very upset. I cannot this with discuss anyone. I understand that a husband can take more than one wife but is that not old fashion in thinking. Should he have not asked for my permission? Is my marriage even legal? We have no intentions of divorcing but I feel that I was lied to. I would have understood and accepted it more if he had confided in me. Can I still do Nikaah? In addition, should not his new wife be entitled to know that he has a wife here in the United States? Please help me! What are my rights under Islam? My husband has his Job here so he will spend the most of his time with me.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

For an Islamic marriage to be valid, some conditions should be met; the most important of which are the presence of the guardian of the wife and two witnesses. So if at the time of your marriage to him you were a woman of the people of the book and the marriage met the required conditions for a correct marriage, then you are considered the wife of this man. It does not matter whether this marriage was called a civil marriage or something else. However, if you were an atheist or not following a revealed religion when you got married, or that one of the conditions for a correct marriage was not met, then the marriage is void and you are not considered his wife.

If we suppose that this marriage was correct, then he is not religiously required to inform you about his marriage to a second wife or inform her of his marriage to you. Since he got married to a second wife, then we think that you should not preoccupy yourself by thinking about it as it could lead (you) to unpleasant consequences. There is no harm in your continuing to live with him and it is an obligation on you to obey him when he calls you to bed unless you are harmed by that (having sexual intercourse with him).

It is an obligation on him to be just between you and his second wife according to his ability. Even if his second wife is far away, he still has to fulfil her rights of spending the night with her and spending on her unless she agrees to forego the matter.

Of course, the above applies if your marriage to him was correct otherwise you are not considered his wife and you have to separate from him and not let him have sexual intercourse with you. In this case you can renew your marriage contract with him by fulfilling its religious requirements.

Finally, we advise you to remain steadfast upon your religion and nurture your children according to Islamic principles so that they will be a comfort to your eyes in this world and in the Hereafter. 

Allaah knows best.