My fiancee and I have found our way back to the Church and have decided to live chastely until we are married. The dilemma is that we have a five-month-old son. It seems more damaging to be separated in this situation than it does to be together. Yet, we fear that our continual sin is good reason to find a way to live apart.
If you are going to be married within the next few months, then it probably will make no difference to your child whether the two of you are spending the night under the same roof. If either of you have family or close friends nearby, perhaps either you alone, or your fiancee and the child, could move in with the family member or close friend until your marriage. If you continue to spend time together with your child each day, the child is not going to be affected by separation at night, and you and your fiancee will not face temptations against chastity.