Did he give a reason for leaving you? Maybe you both can make adjustments in marriage counselling and save your marriage.
I've been married 37 years. My husband and I fell totally in love in the beginning. Then life intruded, we got distracted and things got bad. And on more than one occasion, although we were both faithful to each other. We even separated once for 8 months. He was determined to make a go of it on his own. He discovered that he didn't want to make a go of life without me, and we reconciled, and have not had a major problem since. (Although some small problems, here and there!)
A friend at our new church asked me how long we had been married. I told him, and said we had been through some really hard times together, he replied that he and his wife had too! In fact, I think a lot of long time married couples also have been through some hard times. So bad, that they didn't think the marriage would last.
This is just to tell you, that no marriage, or person is perfect. It is strange to me that two people who love each other would just diverge apart. But, like I said, many do come back together. It is our society, that teaches us that divorce is ok, and nothing wrong with moving on. Being faithful is not just about being "in love." It is about our commitment to Christ, and our loyalty and forgiveness towards our spouse.
But God wants to use these difficult times of life to change us. How can you change for God's glory through this situation? What can you do to be a better follower of Jesus? That is the most important question to ask. And God will use it for good, and perhaps it will make your marriage stronger in the long run.
Praying that God will restore your marriage and your husband, but this time will also bring you closer to God.