What your husband is doing is very wrong, not only in your eyes but in the eyes of God. The Bible is clear: "You shall not commit adultery" (Exodus 20:14). When you were married, you both made a solemn vow before God to be faithful to each other as long as you both would live - and God takes that vow very seriously. But your husband has broken that vow, and from what you say, he shows no signs of regret - let alone repentance.
God gave marriage to us, and His plan was for a husband and wife to live together in complete harmony and trust. The Bible puts it this way: "For this reason a man will leave his father and mother and be united to his wife, and they will become one flesh" (Genesis 2:24). This is why divorce was never part of God's original plan, because it is contrary to His design for marriage.
But we now live in a sinful, imperfect world, and sometimes marriages do break down. Jesus stressed the importance of marriage, but He also taught that divorce was permitted in cases of marital unfaithfulness (see Matthew 19:9).
God loves you, and my prayer is that you will turn to Christ and open your heart and life to Him. Then ask Him to help you know what His will is in this difficult situation. In addition, ask Him to guide you to a pastor or other wise person who can encourage and help you.