If your husband is a Christian then he must know that what he is doing is a sin, and he is going against what the bible says. 1 Corinthians 7:2-3 – “But since there is so much immorality, each man should have his own wife, and each woman her own husband. The husband should fulfill his marital duty to his wife, and likewise the wife to her husband.”
I believe that in some religions this is cause for annulment or divorce, so you don't have to live with a man that doesn't honor you biblically as his wife anymore. Why don't you ask your priest or minister what you can do about your situation according to the word of God..
Lord enlighten this woman as to what she should do in her situation and give her the strength, and comfort she needs. Also the wisdom to understand what your word says concerning her position as a wife in situations like this. Touch her husband's heart and let him see he is not being the husband you intended him to be to his wife. Heal whatever his problem may be, and help him to be a real husband to this woman not just by name. I pray this in Jesus name, amen.